Outline of Center for Emergent Matter Science

Transcription

www.cems.riken.jp
Center for Emergent Matter Science
2 015 -2 016
2-1 Hirosawa, Wako, Saitama 351-0198 Japan
TEL: +81-(0)48-462-1111(Switchboard Number)
FAX: +81-(0)48-462-1554
Email: cems@riken.jp
RIKEN
RIKEN 2015-042
RIKEN
Building a sustainable society that can co-exist in harmony
with the environment
Message
From the Director
The RIKEN Center for Emergent Matter
Science (CEMS) has been launched in
RIKEN unifying the fundamentals of
physics, chemistry, and electronics, and
rallying top-notch leaders as well as
up-and-coming young researchers.
In emergent matter science, we aim at
realizing
emergent phenomena and
functions by manipulating the dynamics
of electrons, spins, and molecules in
materials, and creating materials and
devices for this purpose. Here the word
“emergence” means that qualitatively
new physical properties emerge in
aggregates of many degrees of freedom,
which cannot be expected in simple
assemblies of individual elements. The
three major-fields of CEMS are: (i)
“Strong correlation physics”, exploring
the astonishing functions of materials
with many strongly-entangled electrons;
(ii) Supramolecular/materials chemistry
designing the superstructures of
molecules for novel functions; and (iii)
Quantum
information
electronics
utilizing the quantum entangled states
as state variables.
The mission of RIKEN centers is to solve
challenging and difficult problems,
which requires gathering the individual
abilities of experts. The challenging goal
of CEMS is to explore the energy
functions of electrons in solids and
molecules leading to the “third energy
revolution”.
It is only about 120 years ago when
humans acquired the infrastructure for
accessing electric energy and its
transport system. If the first and second
energy revolutions are defined by the
discoveries of burning energy from fuel
and nuclear reactions, respectively, by
transforming the mechanical energy
from steam engines to electric energy,
the “third energy revolution” should be
the construction of emergent electromagnetism utilizing the electron motions
in solids and molecules, which is
beginning now. Namely, innovative
research based on electrons in solids
and molecules are now going on at an
accelerated pace, following the innovations of semiconductor electronics, solar
cells, and high-temperature superconductivity.
CEMS aims at the discoveries of new
principles/materials which bring about
the discontinuous leap of the figure of
merits, which can be attained only by
fundamental research on materials
science. The value of our research
activities will be judged based on how
much we transmit the new basic
principles toward this goal.
Yoshinori Tokura
Director of Center for Emergent Matter Science
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RIKEN Center for Emergent Matter Science
■ Strong Correlation Physics Division
The Center for Emergent Matter Science (CEMS) brings together leading
scientists in three areas—physics, chemistry, and electronics—to elaborate the
principles of emergent phenomena and to open the path to potential
applications.
Strong Correlation Physics Research Group ........................................... 6
CEMS carries out research in three areas: strongly-correlated materials,
supramolecular functional chemistry, and quantum information electronics. It
incorporates about 200 researchers from around the world, organized into
about 40 research groups and teams.
Strong Correlation Quantum Transport Research Team ...................... 10
There are other leading centers around the world working in each of the three
areas covered by CEMS, but nowhere in the world is there a center that brings
the three together in one place. In order to create a sustainable society that can
co-exist with the natural environment, cooperation between the fields of
physics, chemistry, and electronics is critical.
Bringing these three areas together allows “emergent phenomena” to take
place within the center’ s research as well, making possible breakthroughs in
research that could not be predicted from the outset.
The goal of CEMS is not to develop technologies that can be immediately put
into application. It is not to push existing technologies forward, but rather to
pursue radical new technological principles that will contribute to human
society in five decades or even a century in the future. To do this, it focuses on
basic research and the development of new theories.
Researchers who have pioneered these three fields have been brought
together along with young scientists who are not held back by existing
theories, to work as a team to take on this truly challenging research. This is
the real work of CEMS.
Introduction to EMS
Strong Correlation Theory Research Group ............................................ 7
Strong Correlation Interface Research Group ......................................... 8
Strong Correlation Materials Research Team ......................................... 9
Strong Correlation Quantum Structure Research Team ....................... 11
Emergent Phenomena Measurement Research Team ......................... 12
Quantum Matter Theory Research Team .............................................. 13
Computational Quantum Matter Research Team ................................. 14
First-Principles Materials Science Research Team............................... 15
■ Supramolecular Chemistry Division
Emergent Soft Matter Function Research Group .................................. 16
Emergent Molecular Function Research Group .................................... 17
Emergent Bioinspired Soft Matter Research Team .............................. 18
Emergent Device Research Team .......................................................... 19
Emergent Soft System Research Team ................................................. 20
Emergent Functional Polymers Research Team ................................... 21
Emergent Bioengineering Materials Research Team ............................ 22
Materials Characterization Support Unit ............................................... 23
■ Quantum Information Electronics Division
Quantum Functional System Research Group ...................................... 24
Quantum Condensed Matter Research Group ...................................... 25
“Emergence” refers to the phenomenon in which a number of elements that are brought
together gain properties that could not be predicted from the individual elements. For
example, when a large number of electrons become strongly correlated, they can give
rise to extremely strong electrical and magnetic action that could not be predicted from
the actions of a single electron.
Quantum Condensate Research Team .................................................. 26
Additionally, by linking together a large number of molecules, it is possible to create
materials with new functionalities that were not possessed by the individual molecules.
In this way, when particles such as electrons or molecules gather together, they can
give rise to surprising materials and functions that could not be predicted simply as an
aggregation of the original constituent elements.
Quantum System Theory Research Team ............................................. 30
The science that attempts to elucidate the principles of emergent phenomena and
create new materials and functions based on these principles is known as emergent
matter science. For example, the phenomenon of superconductivity, where metals and
other compounds suddenly lose all their electrical resistance when cooled to a certain
degree, is a phenomenon that arises from the mutual interactions between electrons.
Normally, superconductivity appears at very low temperatures, but if we are able to
design and develop materials that are high-temperature superconductors, it will
become possible to transmit electricity without any loss.
In that way, emergent matter science has the potential to trigger a major revolution in
our lifestyles, and contribute to the achievement of a sustainable society that can
co-exist in harmony with the environment.
Superconducting Quantum Electronics Research Team ...................... 27
Emergent Phenomena Observation Technology Research Team ........ 28
Quantum Nano-Scale Magnetism Research Team ............................... 29
Spin Physics Theory Research Team .................................................... 31
Emergent Matter Science Research Support Team ............................. 32
Quantum Effect Device Research Team ............................................... 33
Quantum Condensed Phases Research Team ..................................... 34
Superconducting Quantum Simulation Research Team ...................... 35
■ Cross-Divisional Materials Research Program
Emergent Spintronics Research Unit .................................................... 36
Dynamic Emergent Phenomena Research Unit .................................... 37
Physicochemical Soft Matter Research Unit ........................................ 38
Quantum Many-Body Dynamics Research Unit ................................... 39
Emergent Photodynamics Research Unit ............................................. 40
Quantum Surface and Interface Research Unit .................................... 41
Cross-Correlated Interface Research Unit ............................................ 42
Computational Materials Function Research Unit ................................ 43
Emergent Superstructure Research Unit .............................................. 44
Emergent Computational Physics Research Unit ................................. 45
Emergent Spectroscopy Research Unit ............................................... 46
Emergent Matter Science Planning Office
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5
Strong Correlation Physics Division
Strong Correlation Physics Research Group
Strong Correlation Theory Research Group
Yoshinori Tokura (Dr.Eng.), Group Director
Naoto Nagaosa
tokura@riken.jp
nagaosa@riken.jp
Research field
Research field
Physics, Engineering, Materials Sciences
Keywords
Keywords
Strongly correlated electron system, Topological
insulators, Spin-orbit interaction, Berry phase physics,
Multiferroics, Skyrmion
Emergent electromagnetism, Magnetoelectric effect,
Spin Hall effect, Interface electrons, Superconductivity
Brief resume
Brief resume
1981 Dr. Eng., University of Tokyo
Topological spin textures and
emergent electromagnetic functions
Nanometric spin texture called "skyrmion". The skyrmion is the idea coined by Tony
Skyrme, a nuclear physicist, to describe a state of nucleon as the topological soliton, It
1986 Associate Professor, University of Tokyo
1994 Professor, Department of Physics, University of Tokyo
1995 Professor, Department of Applied Physics, University of
Tokyo (-present)
2001 Director, Correlated Electron Research Center, AIST
2007 Group Director, Cross-Correlated Materials Research
Group, RIKEN
1983 Research Associate, University of Tokyo
1986 D.Sci., University of Tokyo
Theory of skyrmion dynamics
1998 Professor, University of Tokyo (-present)
Skyrmion- a swirling spin texture of nano-size – is attracting intensive interest aiming at
2007 Team Leader, Theoretical Design Team, RIKEN
can exist as a stable particle protected by topology, but can be also created and
2010 Team Leader, Strong-Correlation Theory Research
Team, RIKEN
has recently been demonstrated that such a kind of topological particle should exist
widely in ubiquitous magnetic solids. The arrows in the figure represent the directions of
2010 Director, Emergent Materials Department, RIKEN
has been an urgent issue. We have revealed the skyrmion dynamics, which is completely
2010 Group Director, Correlated Electron Research Group,
RIKEN
different from the classical Newtonian particle, by the numerical solution of
to the inside, and direct down at the core. This topology cannot be reached via
continuous deformation from the conventional spin orders, meaning that the skyrmion
can be viewed by a topologically protected particle. The skyrmion can carry a fictitious
(emergent) magnetic field working on moving conduction electrons (represented by yellow
balls), and hence causes the topological Hall effect (transverse drift of the current).
Furthermore, the electric current itself can drive the skyrmion. The critical current density
for the drive of skyrmions is around 100A/cm , by five orders of magnitude smaller than
2
2013 Director, RIKEN Center for Emergent Matter Science
(CEMS) (-present)
2013 Group Director, Strong Correlation Physics Research
Group, Strong Correlation Physics Division, RIKEN
CEMS (-present)
2014 Team Leader, Strong Correlation Quantum Transport
Research Team, RIKEN CEMS (-present)
Outline
2001 Team Leader, Theory Team, Correlated Electron
Research Center, National Institute of Advanced
Industrial Science and Technology
the high density and low energy cost magnetic memories of next generation. Skyrmion
2008 AIST Fellow, National Institute of Advanced Industrial
Science and Technology (-present)
the spin (electron's magnetic moment); the spins direct up at the peripheral, swirl in going
(D.Sci.), Group Director
annihilated. Theoretical studies of skyrmion dynamics including its creation/annihilation
Landau-Lifshitz-Gilbert equation combined with the field theoretical analysis. We have
found that (i) Berry phase associated with the solid angle of spins is the origin of the very
small threshold current density for the skyrmion motion, (ii) in constricted geometries such
2013 Deputy Director, RIKEN Center for Emergent Matter
Science (CEMS) (-present)
2013 Group Director, Strong Correlation Theory Research
Group, Division Director, Strong Correlation Physics
Division, RIKEN CEMS (-present)
Outline
as in the circuits, its motion is subject to the dissipation and impurity effect in sharp
contrast to that in the free space, (iii) at the edge of the sample, the skyrmion is
annihilated with the large enough current density, and (iv) the notch structure can produce
skyrmions under the current. These findings provide the theoretical background of
“skyrmionics” using the skyrmions as information carriers.
the conventional value for the drive of magnetic domain walls. These features may favor
the application of skyrmions to innovative spintronics, i.e. toward "skyrmionics".
Skyrmion and conduction electron motion
Publications
1. N. Ogawa, S. Seki, and Y. Tokura, “Ultrafast optical excitation of magnetic skyrmions”, Sci. Rep., 5, 9552
(2015).
2. Y. Tokura, S. Seki, and N. Nagaosa, “Multiferroics of spin origin”, Rep. Prog. Phys., 77, 076501 (2014).
3. X. Z. Yu, Y. Tokunaga, Y. Kaneko, W. Z. Zhang, K. Kimoto, Y. Matsui, Y. Taguchi, and Y. Tokura, “Biskyrmion
states and their current-driven motion in a layered manganite”, Nat. Commun., 5, 3198 (2014).
4. N. Nagaosa, and Y. Tokura, “Topological properties and dynamics of magnetic skyrmions”, Nat.
Nanotechnol., 8, 899 (2013).
5. K. Shibata, X. Z. Yu, T. Hara, D. Morikawa, N. Kanazawa, K. Kimoto, S. Ishiwata, Y. Matsui, and Y. Tokura,
“Towards control of the size and helicity of skyrmions in helimagnetic alloys by spin-orbit coupling”, Nat.
Nanotechnol., 8, 723 (2013).
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O u r g ro u p i n v e s t i g a t e s a v a r i e t y o f e m e r g e n t
phenomena in strongly correlated electron systems,
which cannot be understood within the framework of
conventional semiconductor/metal physics, to
construct a new scheme of science and technology.
In particular, we focus on transport, dielectric and
optical properties in non-trivial spin/orbital structures,
aiming at clarifying the correlation between the
response and the spin/orbital state. In addition, we
investigate electron systems with strong relativistic
spin-orbit interaction, unraveling its impact on
transport phenomena and other electronic properties.
Ta r g e t m a t e r i a l s i n c l u d e h i g h - t e m p e r a t u r e
superconductors, colossal magnetoresistance
systems, multiferroics, topological insulators, and
skyrmion materials.
Core members
(Senior Research Scientist) Xiuzhen Yu
(Special Postdoctoral Researcher) Takashi Kurumaji
(Senior Technical Scientist) Yoshio Kaneko
(Technical Scientist) Chieko Terakura
Skyrmion creation: The notch
structure introduced into the
finite width geometry can result
in the skyrmion creation under
the current. Reproduced from J.
Iwasaki, M. Mochizuki, and N.
Nagaosa, Nature Nanotechnology 8(10) 742-747 (2013).
We study theoretically the electronic states in solids
from the viewpoint of topology and explore new
functions with non-dissipative currents. Combining
first-principles calculations, quantum field theory, and
numerical analysis, we predict and design magnetic,
optical, transport and thermal properties of correlated
electrons focusing on their internal degrees of freedom
such as spin and orbital. In particular, we study
extensively the nontrivial interplay between these
various properties, i.e., cross-correlation, and develop
new concepts such as electron fractionalization and
non-dissipative quantum operation by considering the
topology given by the relativistic spin-orbit interaction
and/or spin textures.
Publications
1. B. J. Yang, E. G. Moon, H. Isobe, and N. Nagaosa, “Quantum criticality of topological phase transitions
in ec-dimensional interacting electronic systems”, Nat. Phys., 10, 774 (2014).
2. M. Mochizuki, X. Z. Yu, S. Seki, N. Kanazawa, W. Koshibae, J. Zang, M. Mostovoy, Y. Tokura, and N.
Nagaosa, “Thermally driven ratchet motion of a skyrmion microcrystal and topological magnon Hall
effect”, Nat. Mater., 13, 241 (2014).
Core members
(Senior Research Scientist)
Andrey Mishchenko, Wataru Koshibae
(Special Postdoctoral Researcher) Yusuke Hama
(Postdoctoral Researcher) Makoto Yamaguchi
3. J. Iwasaki, M. Mochizuki, and N. Nagaosa, “Universal current-velocity relation of skyrmion motion in
chiral magnets”, Nat. Commun., 4, 1463 (2013).
4. M. S. Bahramy, B. J. Yang, R. Arita, and N. Nagaosa, “Emergence of non-centrosymmetric topological
insulating phase in BiTeI under pressure”, Nat. Commun., 3, 679 (2012).
5. Y. Tanaka, M. Sato, and N. Nagaosa, “Symmetry and Topology in Superconductors -Odd-Frequency
Pairing and Edge States-”, J. Phys. Soc. Jpn., 81, 011013 (2012).
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Strong Correlation Interface Research Group
Strong Correlation Materials Research Team
Masashi Kawasaki (Dr.Eng.), Group Director
Yasujiro Taguchi (Dr.Eng.), Team Leader
m.kawasaki@riken.jp
y-taguchi@riken.jp
Research field
Research field
Physics, Engineering, Chemistry, Materials Sciences
Keywords
Keywords
Oxides, Thin films and interfaces, Quantum devices,
Magnetoelectric effect, Photovoltaic effect
Strongly correlated electron system, Magnetocaloric
effect, Thermoelectric effect, Multiferroics, Skyrmion,
High pressure synthesis
Brief resume
Brief resume
1989 D.Eng., University of Tokyo
Novel quantum Hall states realized in
ZnO-based heterostructures
The interface composed of zinc oxide (ZnO) and that doped with Mg (MgZnO) can host
free electrons confined in two-dimensions (2DEG). When a strong magnetic field is
1989 Postdoctoral Fellow, Japan Society for the Promotion of
Science
1989 Postdoctoral Fellow, T. J. Watson Research Center, IBM,
USA
1991 Research Associate, Tokyo Institute of Technology
1997 Associate Professor, Tokyo Institute of Technology
2001 Professor, Tohoku University
2007 Team Leader, Functional Superstructure Team, RIKEN
1993 Researcher, SONY Corporation
Magnetization reversal induced by
an electric field
The electrical control of the magnetization is an important open problem in current solid
state physics, and has also been extensively studied from the viewpoint of applications to
applied normal to the 2DEG plane, the quantum Hall effect (QHE) appears as a
2010 Team Leader, Strong-Correlation Interfacial Device
Research Team, RIKEN
consequence of cyclotron motion of electrons. The discoveries of the integer QHE in Si
2011 Professor, University of Tokyo
to control magnetic information with low power-consumption, and this is expected to lead
and the fractional QHE in GaAs interfaces were both awarded the Nobel Prize in physics.
to innovative devices in future. We have discovered that a (weak-)ferromagnetic and
2013 Group Director, Strong Correlation Interface Research
CEMS (-present)
anisotropy of the rare-earth magnetic moments. We have also succeeded, for the first
In particular, the fractional QHE has been the subject of intensive research in ultra-high
quality GaAs systems to study fundamental electron correlation physics. ZnO has a larger
effective mass and spin susceptibility compared with Si and GaAs, thus giving unique
opportunities to study new and more pronounced electron correlation effects. Because of
the Pauli Exclusion Principle, only odd-denominators are allowed as the indices in the
Outline
spintronics. Specifically, magnetization reversal induced by an electric-field (E) allows us
ferroelectric state shows up in a well-known rare-earth orthoferrite by tuning the
that the domain wall of this system is composed of different order parameters, and that
system, we have observed a novel even-denominator state at 3/2. This state could be
its dynamics is dominated by that of rare-earth magnetic moments. In addition, we have
explained as a state of paired composite Fermions; quasi-particles composed of an
found that PE hysteresis curve can be shifted along E-axis direction by application of a
electron and two flux quanta. We now
magnetic field, demonstrating a novel materials function.
embark on examining the spin
polarization of this state and exploring
the possibility of developing a solid
state device for quantum computation.
1. J. Falson, D. Maryenko, B. Friess, D. Zhang, Y. Kozuka, A. Tsukazaki, J. Smet, and M. Kawasaki,
“Even-denominator fractional quantum Hall physics in ZnO”, Nat. Phys., 11, 347 (2015).
2. R. Yoshimi, A. Tsukazaki, Y. Kozuka, J. Falson, K. S. Takahashi, J. G. Checkelsky, N. Nagaosa, M.
Kawasaki, and Y. Tokura, “Quauntum Hall Effect on Top and Bottom Surface States of Topological Insulator
(Bi1-xSbx)2Te3 Films”, Nat. Commun., 6, 6627 (2015).
3. J. G. Checkelsky, R. Yoshimi, A. Tsukazaki, K. S. Takahashi, Y. Kozuka, J. Falson, M. Kawasaki, and Y.
Tokura, “Trajectory of Anomalous Hall Effect toward the Quantized State in a Ferromagnetic Topological
Insulator”, Nat. Phys., 10, 731 (2014).
4. Z. Sheng, M. Nakamura, W. Koshibae, T. Makino, Y. Tokura, and M. Kawasaki, “Magneto-tunable
photocurrent in manganite based heterojunctions”, Nat. Commun., 5, 4584 (2014).
5. R. Yoshimi, A. Tsukazaki, K. Kikutake, J. G. Checkelsky, K. S. Takahashi, M. Kawasaki, and Y. Tokura,
“Dirac electron states formed at heterointerface between a topological-insulator and a conventional
semiconductor”, Nat. Mater., 13, 253 (2014).
8
Core members
(Senior Research Scientist) Jobu Matsuno,
Kei Takahashi, Masao Nakamura
(Postdoctoral Researcher) Denis Maryenko
2007 Team Leader, Exploratory Materials Team, RIKEN
2010 Team Leader, Strong-Correlation Materials Research
Team, RIKEN
2013 Team Leader, Strong Correlation Materials Research
Team, Strong Correlation Physics Division, RIKEN
Center for Emergent Matter Science (-present)
Outline
antiferromagnetic and antiferroelectric state that compete with each other, by applying E,
demonstrating a dissipation-less quantum electromagnet function. We have also revealed
Publications
2002 Associate Professor, Institute for Materials Research,
Tohoku University
have successfully induced a ferromagnetic and ferroelectric state from an
GaAs, and extensively studied as a candidate quantum computation element. In the ZnO
A paired composite Fermion on a ZnO interface
time, in reversing the magnetization by reversing E in zero magnetic field. In addition, we
fractional QHE. A rare-exception is the even-denominator 5/2 state, observed only in
Artificial interfaces and superlattices are designed and
constructed with the aid of cutting-edge thin film
technology of transition-metal oxides having various
ordered structures in charge, spin and orbital degrees
of freedom of electrons. The responses of these
superstructures to such stimuli as magnetic field,
electrical field and photo irradiation are examined to
elucidate cross-correlated functionalities. These
studies will enable us to create new kinds of devices
such as switches, memories, photovoltaics and
sensors to explore a novel concept of correlated
quantum electronics.
Electric-field-induced magnetization reversal.
Our team aims at obtaining gigantic cross-correlation
responses, understanding their mechanisms, and
developing new functions in strongly-correlated-electron bulk materials, such as transition-metal oxides. To
this end, we try to synthesize a wide range of materials using various methods, including high-pressure
techniques, and investigate their physical properties.
Specific targets are: (1) exploration of new multiferroic
materials; (2) obtaining gigantic magnetoelectric
responses in mutiferroic materials; (3) studying new
magnetotransport phenomena; (4) exploration of new
thermoelectric materials; and (5) obtaining gigantic
magnetocaloric effect.
Publications
1. M. Kriener, A. Kikkawa, T. Suzuki, R. Akashi, R. Arita, Y. Tokura, and Y. Taguchi, “Modification of the
electronic structure and thermoelectric properties of hole-doped tungsten dichalcogenides”, Phys.
Rev. B, 91, 075205 (2015).
2. D. Choudhury, T. Suzuki, Y. Tokura, and Y. Taguchi, “Tuning structural instability toward enhanced
magnetocaloric effect around room temperature in MnCo1-xZnxGe”, Sci. Rep., 4, 7544 (2014).
3. D. Choudhury, T. Suzuki, D. Okuyama, D. Morikawa, K. Kato, M. Takata, K. Kobayashi, R. Kumai, H.
Nakao, Y. Murakami, M. Bremholm, B. B. Iversen, T. Arima, Y. Tokura, and Y. Taguchi, “Evolution of
magnetic and structural transitions and enhancement of magnetocaloric effect in Fe1-xMnxV2O4”, Phys.
Rev. B, 89, 104427 (2014).
Core members
(Research Scientist) Markus Kriener
(Postdoctoral Researcher) Kosuke Karube
(Technical Scientist) Akiko Kikkawa
(Visiting Scientist) Satoshi Shimano
(Company-Sponsored Researcher) Junya Takashima
4. Y. Tokunaga, Y. Taguchi, T. Arima, and Y. Tokura, “Magnetic biasing of a ferroelectric hysteresis loop in
a multiferroic orthoferrite”, Phys. Rev. Lett., 112, 037203 (2014).
5. Y. Tokunaga, Y. Taguchi, T. Arima, and Y. Tokura, “Electric field induced generation and reversal of
ferromagnetic moment in ferrites”, Nat. Phys., 8, 838 (2012).
9
Strong Correlation Quantum Transport
Research Team
Strong Correlation Quantum Structure
Research Team
Yoshinori Tokura (Dr.Eng.), Team Leader
Taka-hisa Arima (Ph.D.), Team Leader
tokura@riken.jp
takahisa.arima@riken.jp
Research field
Research field
Materials Sciences, Physics
Keywords
Keywords
X-ray scattering, Neutron scattering, Electron
diffraction, Structure science, Imaging
Strongly correlated electron system, High-temperature
superconductor, Spin-orbit interaction, Topological
insulators, Interface electronic structure
Brief resume
Brief resume
1988 TORAY Co. Ltd.
1981 Dr. Eng., University of Tokyo
Quantum transport phenomena
in surface Dirac states
The topological insulator is a new class of materials, whose bulk is a three-dimensional
charge-gapped insulator but whose surface hosts a two-dimensional Dirac electron state.
Dirac states are characterized by massless electrons and holes—known as Dirac
fermions whose spins are polarized perpendicular to their crystal momentum. As a result,
the quantum transport phenomena stemming from their charge or spin degrees of
freedom are promising for the applications to low-power consumption electronic devices.
The well-known example for this is the quantum Hall effect (QHE) in which
one-dimensional conducting channel without any dissipation emerges at sample edges.
We established the growth of high quality thin film of (BixSb1-x)2Te3, one of topological
insulators, by means of molecular beam epitaxy (MBE) method. We fabricated “field effect
transistor” structures for electric gating and successfully observed QHE, while changing
the number of electrons in the sample. Furthermore, we synthesized a chromium-doped
Tokyo (-present)
2001 Director, Correlated Electron Research Center, AIST
2007 Group Director, Cross-Correlated Materials Research
Group, RIKEN
2008 AIST Fellow, National Institute of Advanced Industrial
Science and Technology (-present)
2010 Director, Emergent Materials Department, RIKEN
2010 Group Director, Correlated Electron Research Group,
RIKEN
2013 Director, RIKEN Center for Emergent Matter Science
(CEMS) (-present)
2013 Group Director, Strong Correlation Physics Research
CEMS (-present)
2014 Team Leader, Strong Correlation Quantum Transport
Research Team, RIKEN CEMS (-present)
Outline
Analyses of crystal and magnetic structures
with high spatial resolutions
Crystal and magnetic structures have traditionally been determined by x-ray or neutron
diffraction in a homogeneous sample. However, a heterogeneous state often appears in
strongly correlated electron systems. A phase competition can cause phase coexistence.
Symmetry breaking can cause a multi-domain state. A field-induced change in such a
heterogeneous state gives rise to a large physical response. Crystal and magnetic
structure analyses for a small region are hence necessary to understand the microscopic
origin of the large physical response of a strongly correlated electron system.
We have developed several techniques of crystal and magnetic structure analyses with
1991 Research Associate, Faculty of Science, University of
Tokyo
1994 Ph.D. (Science), University of Tokyo
1995 Research Associate, Graduate School of Engineering,
University of Tokyo
1995 Associate Professor, Institute of Materials Science,
University of Tsukuba
(2001-2006 Group Leader, ERATO Tokura Spin Super
Structure Project)
2004 Professor, Institute of Multidisciplinary Research for
Advanced Materials, Tohoku University
2011 Professor, Graduate School of Frontier Sciences,
University of Tokyo (-present)
2007 Team Leader, Spin Order Research Team, RIKEN
SPring-8 Center
2013 Team Leader, Strong Correlation Quantum Structure
Research Team, RIKEN Center for Emergent Matter
Science (-present)
a very high spatial resolution by focusing high-energy electron beams or synchrotron
x-ray beams. Convergent-beam electron diffraction and Lorentz electron microscopy
Outline
have been applied to a chiral magnet MnSi to study the relation between the
crystallographic chirality and the helicity of magnetic skyrmions. A micro-probe x-ray
compound Crx(Bi1-ySby)2-xTe3, which shows a spontaneous gap opening in a Dirac state
diffraction study has been performed on a VO 2 film, and revealed that the c-axis is
due to the ferromagnetic ordering. As a result, we observed the quantum anomalous Hall
elongated at the region where
effect (QAHE), which is a quantum Hall state realized at zero magnetic field. We now
an electric field induces an
embark on the observation or control of the quantum transport at a ferromagnetic domain
insulator-to-metal transition.
wall as the edge state in the magnetic topological insulators.
Because the c-axis shrinks
when the film changes into a
metal by warming, the two
Schematic of the quantum Hall effect on the surface of a topological insulator
Publications
1. R. Yoshimi, A. Tsukazaki, Y. Kozuka, J. Falson, K. S. Takahashi, J. G. Checkelsky, N. Nagaosa, M.
Kawasaki, and Y. Tokura, “Quantum Hall effect on top and bottom surface states of topological insulator
(Bi1-xSbx)2Te3 films”, Nat. Commun., 6, 6627 (2015).
2. J. G. Checkelsky, R. Yoshimi, A. Tsukazaki, K. S. Takahashi, Y. Kozuka, J. Falson, M. Kawasaki, and Y.
Tokura, “Trajectory of the anomalous Hall effect towards the quantized state in a ferromagnetic topological
insulator”, Nat. Phys.,10, 731 (2014).
3. R. Yoshimi, A. Tsukazaki, K. Kikutake, J. G. Checkelsky, K. S. Takahashi, M. Kawasaki, and Y. Tokura,
“Dirac electron states formed at the heterointerface between a topological insulator and a conventional
semiconductor”, Nat. Mater., 13, 253 (2014).
4. H. Murakawa, M. S. Bahramy, M. Tokunaga, Y. Kohama, C. Bell, Y. Kaneko, N. Nagaosa, H. Y. Hwang,
and Y. Tokura, “Detection of Berry’s phase in a bulk Rashba semiconductor”, Science, 342, 1490 (2013).
5. S. Chakraverty, T. Matsuda, H. Wadati, J. Okamoto, Y. Yamasaki, H. Nakao, Y. Murakami, S. Ishiwata, M.
Kawasaki, Y. Taguchi, Y. Tokura, and H. Y. Hwang, “Multiple helimagnetic phases and topological Hall
effect in epitaxial thin films of pristine and Co-doped SrFeO3”, Phys. Rev. B, 88, 220405(R) (2013).
10
We study various kinds of quantum transport
phenomena which emerge in bulk materials and at
hetero-interfaces of thin films, focusing on electron
systems with strong correlation and/or strong
spin-orbit interactions. Specifically, we try to clarify
quantum states of Dirac electrons at surface/interfaces
of topological insulators as well as in bulk Rashba
system with broken inversion symmetry, by observing
Landau level formation, quantum (anomalous) Hall
effect, and various quantum oscillation phenomena at
low temperatures and in high magnetic fields. Also, we
synthesize high-temperature superconducting
cuprates in bulk forms and various transition-metal
oxides thin films, and measure transport properties
under high pressure or high magnetic-field, aiming at
increasing superconducting transition temperature and
at finding novel magneto-transport properties.
Core members
Ayako Yamamoto, Minoru Kawamura
(Junior Research Associate) Ken Okada
metallic phases are completely
different from each other in
electronic structure.
Change in crystal structure with the electric-field-induced
insulator-metal transition in VO2 film
Publications
Publications
1. S. Tardif, S. Takeshita, H. Ohsumi, J. Yamaura, D. Okuyama, Z. Hiroi, M. Takata, and T. Arima,
“All-In-All-Out Magnetic Domains: X-Ray Diffraction Imaging and Magnetic Field Control”, Phys. Rev.
Lett., 114, 147205 (2015).
2. T. Nakajima, Y. Tokunaga, V. Kocsis, Y. Taguchi, Y. Tokura, and T. Arima, “Uniaxial-Stress Control of
Spin-Driven Ferroelectricity in Multiferroic Ba 2CoGe 2O7”, Phys. Rev. Lett., 114, 067201 (2015).
3. D. Okuyama, K. Shibuya, R. Kumai, T. Suzuki, Y. Yamasaki, H. Nakao, Y. Murakami, M. Kawasaki, Y.
Taguchi, Y. Tokura, and T. Arima, “X-ray study of metal-insulator transitions induced by W doping and
photoirradiation in VO2 films”, Phys. Rev. B, 91, 064101 (2015).
Strongly correlated electron systems may exhibit
various interesting emergent phenomena such as
superconductivity, colossal magneto-resistance, and
giant magneto-electric effects. These emergent
phenomena are directly associated with the spatial
distributions as well as the spatial and temporal
fluctuations of atoms, electron density, and spin
density. To reveal these phenomena, we perform
crystallographic and magnetic structure analyses,
spectroscopies, and microscopies by using
synchrotron x-rays, neutrons, and high-energy
electron beams.
Core members
(Postdoctoral Researcher)
Taro Nakajima, Daisuke Morikawa
4. D. Okuyama, M. Nakano, S. Takeshita, H. Ohsumi, S. Tardif, K. Shibuya, T. Hatano, H. Yumoto, T.
Koyama, H. Ohashi, M. Takata, M. Kawasaki, T. Arima, Y. Tokura, and Y. Iwasa, “Gate-tunable gigantic
lattice deformation in VO2”, Appl. Phys. Lett., 104, 023507 (2014).
5. Y. Tokunaga, Y. Taguchi, T. Arima, Y. Tokura, “Magnetic Biasing of a Ferroelectric Hysteresis Loop in a
Multiferroic Orthoferrite”, Phys. Rev. Lett., 112, 037203 (2014).
11
Emergent Phenomena Measurement
Research Team
Quantum Matter Theory Research Team
Tetsuo Hanaguri (D.Eng.), Team Leader
Akira Furusaki (D.Sci.), Team Leader
hanaguri@riken.jp
furusaki@riken.jp
Research field
Research field
Physics, Materials Science
Keywords
Keywords
Scanning tunneling microscopy, Superconductivity,
Topological insulators
Electron correlation, Frustrated quantum magnets,
Topological insulators, Superconductivity
Brief resume
Brief resume
1993 D.Eng., Tohoku University
Direct imaging of massless electrons
at the surface of a topological insulator
Topological insulators are a new phase of matter which was discovered recently.
Although it is an insulator in the bulk, a topological insulator possesses a metallic surface
1993 Research Associate, Department of Basic Science, The
University of Tokyo
1999 Associate Professor, Department of Advanced Materials
Science, The University of Tokyo
2004 Senior Research Scientist, Magnetic Materials
Laboratory, RIKEN
2013 Team Leader, Emergent Phenomena Measurement
Research Team, Strong Correlation Physics Division,
RIKEN Center for Emergent Matter Science (-present)
Outline
Modern electronics is based on the band theory that describes quantum mechanical
motion of electrons in a solid. The band theory can explain properties of metals, insulators
revealed some important physics which was missed in the standard band theory. Namely,
information. However, the experimental understanding of massless electrons is still
the geometric (Berry) phase of electron wave functions can have a nontrivial topological
elusive.
structure in momentum space, and this leads to a topological insulator. In addition,
superconductors with gapped quasiparticle excitations can be a topological
Using scanning tunneling microscope, our team succeeded in imaging the nano-scale
of the cyclotron motion drifts around the charged defect, resulting in an “electron ring”.
We constructed a general theory that can classify TIs and TSCs in terms of generic
We found that the unique character of massless electrons manifests itself in the internal
symmetries. This theory shows that in every spatial dimension there are three types of
structure of the electron ring. The observed internal structure is related to the spin
TIs/TSCs with an integer topological index and two types of TIs/TSCs with a binary
1. Y.-S. Fu, M. Kawamura, K. Igarashi, H. Takagi, T. Hanaguri, and T. Sasagawa,“Imaging the two-component
nature of Dirac–Landau levels in the topological surface state of Bi2Se3”, Nat. Phys., 10, 815 (2014).
2. T. Hanaguri, K. Kitagawa, K. Matsubayashi, Y. Mazaki, Y. Uwatoko, and H.Takagi, “Scanning tunneling
microscopy/spectroscopy of vortices in LiFeAs”, Phys. Rev. B, 85, 214505 (2012).
3. Y. Kohsaka, T. Hanaguri, M. Azuma, M. Takano, J.C. Davis, and H. Takagi, “Visualization of the emergence
of the pseudogap state and the evolution to superconductivity in a lightly hole-doped Mott insulator”, Nat.
Phys., 8, 534 (2012).
4. T. Hanaguri, K. Igarashi, M. Kawamura, H. Takagi, and T. Sasagawa, “Momentum-resolved Landau-level
spectroscopy of Dirac surface state in Bi2Se3”, Phys. Rev. B, 82, 081305(R) (2010).
5. T. Hanaguri, S. Niitaka, K. Kuroki, and H. Takagi, “Unconventional s-Wave Superconductivity in Fe(Se,Te)”,
Science, 328, 474 (2010).
1995 Research Associate, Department of Applied Physics,
University of Tokyo
1996 Associate Professor, Yukawa Institute for Theoretical
Physics, Kyoto University
2002 Chief Scientist, Condensed Matter Theory Laboratory,
RIKEN (-present)
2013 Team Leader, Quantum Matter Theory Research Team,
Strong Correlation Physics Division, RIKEN Center for
Emergent Matter Science (-present)
Outline
topological index. Furthermore, we developed a theory classifying TIs/TSCs with a mirror
distribution and will give us an important clue for future spintronics applications.
Publications
1993 Postdoctoral Associate, Massachusetts Institute of
Technology, USA
topological superconductors (TSCs) in nature.
focus on imaging in a magnetic field, where electrons exhibit cyclotron motion. The center
”Electron rings” at
different energies
1993 Ph.D., University of Tokyo
superconductor. In principle there are various types of topological insulators (TIs) and
spatial structure of massless electrons at the surface of a topological insulator Bi2 Se3 . We
12
Classifying topological insulators and
topological superconductors
and semiconductors, and led to the invention of transistors. However, recent studies
where electrons lose their mass. The surface state is expected to serve as a base of
spintronics application, because spins of massless electrons can be used to handle
University of Tokyo
We experimentally study electronic states related to
emergent phenomena in electron systems, such as
high-temperature superconductivity and topological
quantum phenomena. For this purpose, we use
scanning tunneling microscopes working under
combined extreme conditions of very low
temperatures, high magnetic fields and ultra-high
vacuum. Modern scanning-tunneling-microscopy
technology enables us to obtain a “map of the
electronic state” with atomic-scale spatial resolution.
We make and analyze the maps of various materials
and establish the relationships between material
properties and electronic states. We also pursue the
development of novel measurement techniques to
discover new emergent phenomena in condensed
matter.
Core members
Katsuya Iwaya, Yuhki Kohsaka
(Postdoctoral Researcher) Tadashi Machida
(Student Trainee)
Tatsuya Watashige, Kensuke Matsuoka
symmetry.
A coffee mug and a donut are equivalent in topology because they
can be continuously deformed from one to the other.
We investigate novel quantum phases of many-electron systems in solids which emerge as a result of
strong electron correlation and quantum effects. We
theoretically study electronic properties of these new
phases (such as transport and magnetism) and critical
phenomena at phase transitions. Specifically, we
study topological insulators and superconductors,
frustrated quantum magnets, and other strongly
correlated electron systems in transition metal oxides
and molecular conductors, etc. We construct effective models for electrons in these materials and unveil
their various emergent phases by solving quantum
statistical mechanics of these models using both
analytical and numerical methods.
Publications
1. T. Morimoto, and A. Furusaki, “Topological classification with additional symmetries from Clifford
algebras”, Phys. Rev. B, 88, 125129 (2013).
2. K. Yoshimi, H. Seo, S. Ishibashi, and S. E. Brown, “Tuning the magnetic dimensionality by charge
ordering in the molecular TMTTF salts”, Phys. Rev. Lett., 108, 096402 (2012).
3. T. Momoi, P. Sindzingre, and K. Kubo, “Spin nematic order in multiple-spin exchange models on the
triangular lattice”, Phys. Rev. Lett., 108, 057206 (2012).
Core members
Tsutomu Momoi, Shigeki Onoda, Hitoshi Seo
(Special Postdoctoral Researcher) Daisuke Takahashi
(Postdoctoral Researcher) Troels Bojesen
4. S. Onoda and Y. Tanaka, “Quantum fluctuations in the effective pseudospin-1/2 model for magnetic
pyrochlore oxides”, Phys. Rev. B, 83, 094411 (2011).
5. S. Ryu, A. P. Schnyder, A. Furusaki, and A. W. W. Ludwig, “Topological insulators and superconductors:
ten-fold way and dimensional hierarchy”, New J. Phys., 12, 065010 (2010).
13
Computational Quantum Matter
Research Team
First-Principles Materials
Science Research Team
Seiji Yunoki (D.Eng.), Team Leader
Ryotaro Arita (D.Sci.), Team Leader
yunoki@riken.jp
arita@riken.jp
Research field
Research field
Physics, Materials Sciences
Physics, Materials Science
Keywords
Keywords
Strongly correlated electron system, Magnetism,
Superconductivity, Computational condensed matter
physics
First-principles calculations, Theoretical materials
design, Strongly correlated electron systems
Brief resume
Brief resume
2000 D. Sci., Univerisity of Tokyo
1996 D.Eng., Nagoya University
Mechanism of novel insulating state and
possible superconductivity induced by
a spin-orbit coupling
Electrons in solids are moving around, affected by the Coulomb interaction,
electron-lattice interaction, and spin-orbit interaction, which induces different behaviors
characteristic of each material. Recently, the study for the spin-orbit coupling has greatly
progressed and attracted much attention. In the 5d transition metal oxide Sr2 IrO4 , the spin
and orbital degrees of freedom are strongly entangled due to the large spin-orbit coupling
and the novel quantum state is formed. Sr 2 IrO 4 is also expected to be a possible
superconducting material with a great deal of similarities to the parent compound of
cuprate high-temperature superconductivity
We have studied the detailed electronic properties of a 3-orbital Hubbard model for Sr2
1996 Postdoctoral Researcher, National High Magnetic Field
Laboratory, USA
1999 Postdoctoral Researcher, Materials Science Center,
Groningen University, Netherlands
2001 Postdoctoral Researcher, International School for
Advanced Studies, Italy
Development of density functional theory
for unconventional superconductors
Prediction or materials design of high temperature superconductivity is a true Holy Grail
2006 Long-Term Researcher and Research Assistant
Professor, Oak Ridge
National Laboratory and University of Tennessee, USA
of condensed matter theory. To achieve this goal, we need to develop a predictive
2008 Associate Chief Scientist, Computational Condensed
Matter Physics Laboratory, RIKEN (-present)
ductivity is mediated by phonons, plasmons, excitons, spin fluctuations, and so on. In
method to calculate transition temperatures of superconductors. In general, supercon-
2010 Team Leader, Computational Materials Research Team,
RIKEN Advance Institute for Computational Science
(-present)
2005, density functional theory for phonon-mediated conventional superconductors was
2013 Team Leader, Computational Quantum Matter Research
Team, RIKEN Center for Emergent Matter Science
(-present)
metals, MgB2 , CaC6 , and so on, However, for unconventional superconductors such as
successfully formulated and has been applied to various superconductors such as simple
2000 Research Associate, Department of Physics, University
of Tokyo
2004 Postdoctoral Researcher, Max Planck Institute for Solid
State Research
2006 Research Scientist/Senior Research Scientist,
Condensed Matter Theory Laboratory, RIKEN
2008 Associate Professor, Department of Applied Physics,
University of Tokyo
2011 PRESTO, Japan Science and Technology Agency
2014 Team Leader, First-Principles Materials Science
Science (-present)
Outline
high Tc cuprates, iron-based superconductors and so on, development of density functional theory has remained a big challenge. We formulated a scheme for the plasmon
Outline
mechanism, a prototypical unconventional pairing mechanism whose history dates back
to late 70s. We applied our new method to one of the most elemental high temperature
IrO4 with several computational methods. Our calculations have clearly shown that the
superconductors, lithium under high pressures. We obtained an excellent agreement
ground state of this material is an effective total angular momentum J eff=1/2
between theory and experiment.
antiferromagnetic insulator, where Jeff is “pseudospin”,formed by spin and orbital degrees
of freedom due to the strong spin-orbit coupling (x-AFI in Fig. (a)). We have also proposed
that the dx2-y2 -wave “pseudospin singlet” superconductivity (SC in Fig. (b)) is induced by
electron doping into the
Jeff=1/2 antiferromagnetic
insulator Sr2IrO4.
Ground state phase diagram of 3-orbital Hubbard model with a
spin-orbit coupling. (a) Electron density n=5, (b) n>5.
Publications
1. H. Watanabe, T. Shirakawa, and S. Yunoki, “Theoretical study of insulating mechanism in multiorbital
Hubbard models with a large spin-orbit coupling: Slater versus Mott scenario in Sr2IrO4”, Phys. Rev. B, 89,
165115 (2014).
2. S. Hikino, and S. Yunoki, “Long-range spin current driven by superconducting phase difference in a
Josephson junction with double layer ferromagnets”, Phys. Rev. Lett., 110, 237003 (2013).
3. A. Annadi, Q. Zhang, X. Renshaw Wang, N. Tuzla, K. Gopinadhan, W. M. Lu, A. Roy Barman, Z. Q. Liu, A.
Srivastava, S. Saha, Y. L. Zhao, S. W. Zeng, S. Dhar, E. Olsson, B. Gu, S. Yunoki, S. Maekawa, H.
Hilgenkamp, T. Venkatesan, and A. Ariando, “Anisotropic two-dimensional electron gas at the
LaAlO3/SrTiO3 (110) interface”, Nat. Commun., 4, 1838 (2013).
4. H. Watanabe, T. Shirakawa, and S. Yunoki, “Monte Carlo study of an unconventional superconducting
phase in Iridium oxide Jeff = 1/2 Mott insulators induced by carrier doping”, Phys. Rev. Lett., 110, 027002
(2013).
5. S. Sorella, Y. Otsuka, and S. Yunoki, “Absence of a Spin Liquid Phase in the Hubbard Model on the
Honeycomb Lattice”, Sci. Rep., 2, 992 (2012).
14
Electrons in solids are in motion within the energy
band reflecting the lattice structure of each material.
The Coulomb interaction, electron-lattice interaction,
and spin-orbit interaction have nontrivial effects on the
motion of electrons and induce various interesting
phenomena. Our aim is to elucidate the emergent
quantum phenomena induced by cooperation or
competition of these interactions, using
state-of-the-art computational methods for condensed
matter physics. Our current focus is on various
functional transition metal oxides, topological
materials, and heterostructures made of these
materials. Our research will lead not only to clarify the
mechanism of quantum phenomena in existent
materials but also to propose novel materials.
Core members
(Contract Researcher) Hiroshi Watanabe
(Research Scientist) Tomonori Shirakawa
Superconducting transition temperature of Li under pressures. The present formalism which
considers the phonon-plasmon cooperation shows a better agreement with the experiment.
Publications
1. Y. Nomura, K. Nakamura, and R. Arita, “Effect of electron-phonon interaction on orbital fluctuations in
iron-based superconductors”, Phys. Rev. Lett., 112 027002 (2014).
2. R. Akashi, and R. Arita, “Development of density functional theory for plasmon-assisted superconducting
state: Application to Lithium under high pressures”, Phys. Rev. Lett., 111 057006 (2013).
3. H. Ikeda, M-T.Suzuki, R. Arita, T. Takimoto, T. Shibauchi, and Y. Matsuda, “Emergent rank-5 nematic
order in URu 2Si2”, Nat. Phys., 8, 528 (2012).
By means of first-principles methods, our team studies
non-trivial electronic properties of materials which lead
to new ideas/notions in condensed matter physics or
those which have potential possibilities as unique
functional materials. Especially, we are currently
interested in strongly correlated/topological materials
such as high Tc cuprates, iron-based
s u p e rc o n d u c t o r s , o r g a n i c s u p e rc o n d u c t o r s ,
carbon-based superconductors, 5d transition metal
compounds, heavy fermions, giant Rashba systems,
topological insulators, zeolites, and so on. We aim at
predicting unexpected phenomena originating from
many-body correlations and establishing new guiding
principles for materials design. We are also interested
in the development of new methods for ab initio
electronic structure calculation.
Core members
(Senior Research Scientist) Takashi Koretsune
(Research Scientist) Shiro Sakai, Michi-To Suzuki
4. R. Arita, J. Kunes, A.V. Kozhevnikov, A.G. Eguiluz, and M. Imada, “Ab initio Studies on the Interplay
between Spin-Orbit Interaction and Coulomb Correlation in Sr2IrO4 and Ba 2IrO4”, Phys. Rev. Lett., 108,
086403 (2012).
5. M. S. Bahramy, B. -J. Yang, R. Arita, and N. Nagaosa, “Emergence of non-centrosymmetric topological
insulating phase in BiTeI under pressure”. Nat. Commun., 3, 679 (2012).
15
Supramolecular Chemistry Division
Emergent Soft Matter Function Research Group
Emergent Molecular Function Research Group
Takuzo Aida (Dr.Eng.), Group Director
Kazuo Takimiya (Dr.Eng.), Group Director
takuzo.aida@riken.jp
takimiya@riken.jp
Research field
Research field
Chemistry, Engineering, Materials Sciences
Chemistry, Materials Sciences
Keywords
Keywords
Soft material, Molecular design, Self-assembly, Energy
conversion, Biomimetics, Stimuli-responsive material,
Electronic material, Photoelectric conversion material,
Environmentally friendly material
Organic semiconductor, Pi-Electronic compound,
Semiconducting polymers, Organic field-effect
transistor, Organic solar cells
Brief resume
Brief resume
Chain-growth supramolecular polymerization
Over the last decade, significant progress in supramolecular polymerization has had a
1984 Research Assistant / Lecturer, University of Tokyo
substantial impact on the design of functional soft materials. However, despite recent
2000 Project Leader, ERATO Aida Nanospace Project, Japan
Science and Technology Corporation
advances, most studies are still based on a preconceived notion that supramolecular
2007 Group Director, Responsive Matter Chemistry &
Engineering Research Group, RIKEN
polymerization follows a step-growth mechanism. We recently realized the first
chain-growth supramolecular polymerization by designing metastable monomers with a
shape-promoted intramolecular hydrogen-bonding network. The monomers are
conformationally restricted from spontaneous polymerization at ambient temperatures but
begin to polymerize with characteristics typical of a living mechanism upon mixing with
tailored initiators. The chain growth occurs stereoselectively and therefore enables optical
resolution of a racemic monomer. We believe that it may give rise to a paradigm shift in
precision macromolecular engineering.
2010 Group Director, Functional Soft Matter Research Group,
RIKEN
2011 Team Leader, Photoelectric Conversion Research Team,
RIKEN
2013 Group Director, Emergent Soft Matter Function
Research Group, Division Director, Supramolecular
Chemistry Division, RIKEN CEMS (-present)
Outline
1994 Ph.D., Hiroshima University
New semiconducting polymers enabling
high performance in OPVs.
Our group has developed several new building blocks for constructing semiconducting
polymers and has recently been working with a particular type of polymer called
PNNT-DT, consisting of naphthodithiophene- (NDT) and naphthobisthiadiazole- (NTz)
1994 Research Associate, Hiroshima University
1997 Visiting Researcher, Odense University, Denmark
2003 Associate Professor, Hiroshima University
2007 Professor, Hiroshima University
2012 Team Leader, Emergent Molecular Function Research
Team, RIKEN
2013 Group Director, Emergent Molecular Function Research
Group, Supramolecular Chemistry Division, RIKEN
CEMS (-present)
building blocks, both of which were developed in our group. Although PNNT-DT can
afford OPVs showing moderate power conversion efficiency (~5.5%), its low solubility
Outline
decreases its processability. Thus, we recently attached additional alkyl groups to the
polymer and found that not only the solubility of the polymer was enhanced, but also
significantly improved the power-conversion efficiencies of solar cells made with these
polymers. In these solar cells, the new alkylated polymers were arranged so that the
polymer chains lay flat in stacks on the surface rather than aligned perpendicular to it.
This causes the charge carriers, electrons and holes, to move perpendicular to the
surface rather than parallel, improving the power-conversion efficiency. This drastic
change in orientation produced solar cells with an efficiency of up to 8.2%, which is
among the highest for OPVs with these newly developed semiconducting polymers.
Schematic illustration of chain-growth supramolecular polymerization
Publications
1. S. Chen, Y. Itoh, T. Masuda, S. Shimizu, J. Zhao, J. Ma, S. Nakamura, K. Okuro, H. Noguchi, K. Uosaki,
and T. Aida, “Subnanoscale hydrophobic modulation of salt bridges in aqueous media”, Science, 348, 555
(2015).
2. J. Kang, D. Miyajima, T. Mori, Y. Inoue, Y. Itoh, and T. Aida, “A rational strategy for the realization of
chain-growth supramolecular polymerization”, Science, 347, 646 (2015).
3. S. Sim, D. Miyajima, T. Niwa, H. Taguchi, and T. Aida, “Tailoring Micrometer-Long High-Integrity 1D Array
of Superparamagnetic Nanoparticles in a Nanotubular Protein Jacket and Its Lateral Magnetic Assembling
Behavior”, J. Am. Chem. Soc., 137, 4658 (2015).
4. M. Liu, Y. Ishida, Y. Ebina, T. Sasaki, T. Hikima, M. Takata, and T. Aida, “An anisotropic hydrogel with
electrostatic repulsion between cofacially aligned nanosheets”, Nature, 517, 68 (2015).
5. T. Fukino, H. Joo, Y. Hisada, M. Obana, H. Yamagishi, T. Hikima, M. Takata, N. Fujita, and T. Aida,
“Manipulation of Discrete Nanostructures by Selective Modulation of Noncovalent Forces”, Science, 344,
499 (2014).
16
With world's focus on environment and energy issues,
our group aims to establish a novel principle of
material sciences addressing these problems, through
the development of unprecedented functional
materials with precisely controlled structure and
properties at molecular to nanoscale levels. The main
research subjects include (1) the development of novel
organic catalysts consisting only of ubiquitous
elements for high efficient water photolysis, (2) the
development of the solution-processable organic
ferroelectric materials for the application to memory
d e v i c e s , a n d ( 3 ) t h e d e v e l o p m e n t o f p re c i s e
supramolecular polymerizations.
Core members
(Special Postdoctoral Researcher) Daigo Miyajima
(Student Trainee) Song Zhang, Taehoon Kim,
Seunghyun Sim, Jiheong Kang, Hiroki Arazoe,
Yuki Omata, Shigeru Sakamoto, Yukinaga Suzuki,
Toshiaki Takeuchi
(Technical Staff) Emiko Sato, Atsuko Nihonyanagi
Drastic change in polymer orientation and improved solar cell performances by alkylation.
Adapted from “J. Am. Chem. Soc. 2013, 135, 8834–8837.” with permission (© 2013
American Chemical Society).
Publications
1. K. Takimiya, I. Osaka, T. Mori, and M. Nakano, “Organic Semiconductors Based on [1]Benzothieno
[3,2-b][1]benzothiophene Substructure”, Acc. Chem. Res., 47, 1493 (2014).
2. I. Osaka, M. Saito, T. Koganezawa, and K. Takimiya, “Thiophene-Thiazolothiazole Copolymers:
Significant Impact of Side Chain Composition on Polymer Orientation and Solar Cell Performances”,
Adv. Mater., 26, 331 (2014).
3. I. Osaka, T. Kakara, N. Takemura, T. Koganezawa, and K. Takimiya, “Naphthodithiophene Naphthobisthiadiazole Copolymers for Solar Cells: Alkylation Drives the Polymer Backbone Flat and
Promotes Efficiency”, J. Am. Chem. Soc., 135, 8834 (2013).
Our goal is to develop functional organic materials
utilized in optoelectronic devices, such as organic
field-effect transistors (OFETs) and organic solar cells
(organic photovoltaics, OPVs). To this end, our group
develops new organic materials, which can be
designed and synthesized in order to have appropriate
molecular and electronic structures for target
functionalities. Our recent achievements are: 1) the
development of high-performance molecular
semiconductors applicable to OFETs with the highest
mobilities, and 2) the development of versatile
semiconducting polymers that can be utilized in
high-performance solution-processed OFETs and
OPVs.
Core members
(Senior Research Scientist) Itaru Osaka
Masahiro Nakano, Masahiko Saito,
Hiroyoshi Sugino, Wang Chengyuan
(Junior Research Associate) Masanori Sawamoto
(Technical Staff)
Kazuaki Kawashima, Noriko Takemura,
Yasuhito Suzuki, Mizue Yuki
4. Y. Fukutomi, M. Nakano, Jian-Yong Hu, I. Osaka, and K. Takimiya, “Naphthodithiophenediimide (NDTI):
Synthesis, Structure, and Applications”, J. Am .Chem. Soc., 135, 11445 (2013).
5. K. Takimiya, S. Shinamura, I. Osaka, and E. Miyazaki, “Thienoacene-based Organic Semiconductors”,
Adv. Mater., 23, 4347 (2011).
17
Emergent Bioinspired Soft Matter
Research Team
Emergent Device Research Team
Yasuhiro Ishida (D.Eng.), Team Leader
Yashihiro Iwasa (D.Eng.), Team Leader
y-ishida@riken.jp
iwasay@riken.jp
Research field
Research field
Keywords
Keywords
Field effect transistor, Materials science at high electric
field, Two-dimensional electron system, Thermoelectric
effect, Superconductivity
Self-assembly, Biomimetics, Soft material,
Stimuli-responsive material, Environmentally friendly
material
Brief resume
Brief resume
Synthetic hydrogel like cartilage,
but with a simpler structure
- Potential as artificial cartilage and anti-vibration materials Electrostatic and magnetic repulsive forces are used in various places, as in maglev trains,
2001 Assistant Professor, Graduate School of Frontier
Sciences, University of Tokyo
2002 Assistant Professor, Graduate School of Engineering,
University of Tokyo
2007 Lecturer, Graduate School of Engineering, University of
Tokyo
2007 Researcher, PRESTO, Japan Science and Technology
Agency
vehicle suspensions or non-contact bearings etc. However, design of polymer materials,
2009 Team Leader, Nanocomposite Soft Materials Engineering
Team, RIKEN
such as rubbers and plastics, has focused overwhelmingly on attractive interactions for their
2010 Team Leader, Bioinspired Material Research Team,
RIKEN
reinforcement, while little attention has been given to the utility of internal repulsive forces.
Nevertheless, in nature, articular cartilage in animal joints utilizes an electrostatically repulsive
force for insulating interfacial mechanical friction even under high compression.
We discovered that when nanosheets of unilamellar titanate, colloidally dispersed in an
2013 Team Leader, Emergent Bioinspired Soft Matter
Research Team, Supramolecular Chemistry Division,
Outline
aqueous medium, are subjected to a strong magnetic field, they align cofacial to one
1986 Ph. D., University of Tokyo
Switching the state of matter
Strongly-correlated materials, whose electrons interact with each other to produce
unusual and often useful properties, have attracted growing attention. One of these
University of Tokyo
1991 Lecturer, Department of Applied Physics, University of
Tokyo
1994 Associate Professor, School of Materials Science, Japan
Advanced Institute of Science and Technology
properties is triggered in phase transitions. Applying small external stimuli such as
2001 Professor, Institute for Materials Research, Tohoku
University
magnetic field, electric field, and pressure can induce a very large change in physical
2010 Professor, Quantum-Phase Electronics Center, University
of Tokyo (-present)
properties.
We have created the world's first transistor that harnesses this unique property. The
electric-double layer transistor (EDLT) of vanadium dioxide (VO2 ) drives localized electrons
within the bulk to delocalize, greatly magnifying the change of electronic phase (see left
Figure). On the other hand, EDLT uncovered a hidden insulating phase at the half-doped
manganite Pr0.5 Sr0.5 MnO3 (right Figure). Electric-field induced bulk transformation of this
2010 Team Leader, Strong-Correlation Hybrid Materials
Research Team, RIKEN
2013 Team Leader, Emergent Device Research Team,
Supramolecular Chemistry Division, RIKEN Center for
Outline
kind is impossible using conventional semiconductor-based electronics and suggests a
another, where large and anisotropic electrostatic repulsion emerges between the
wide range of potential applications.
nanosheets. This magneto-induced temporal structural ordering can be fixed by
transforming the dispersion into a hydrogel. The anisotropic electrostatics thus embedded
allows the hydrogel to show unprecedented mechanical properties, where the hydrogel easy
deforms along a shear force applied parallel to the nanosheet plane but is highly resistive
against a compressive force applied orthogonally.
The concept of embedding repulsive electrostatics in a composite material, inspired from
articular cartilage, will open new possibilities for developing soft materials with unusual
functions.
Hydrogel embedded
with an anisotropic
electrostatic repulsive
force
Publications
1. M. Liu, Y. Ishida, Y. Ebina, T. Sasaki, T. Hikima, M. Takata, and T. Aida, “An anisotropic hydrogel with
electrostatic repulsion between cofacially aligned nanosheets”, Nature, 517, 68 (2015).
2. L. Wu, M. Ohtani, M. Takata, A. Saeki, S. Seki, Y. Ishida, and T. Aida, “Magnetically induced anisotropic
orientation of graphene oxide locked by in situ hydrogelation”, ACS Nano, 8, 4640 (2014).
3. M. Liu, Y. Ishida, Y. Ebina, T. Sasaki, and T. Aida, “Photolatently modulable hydrogels using unilamellar
titania nanosheets as photocatalytic crosslinkers”, Nat. Commun., 4, 2029 (2013).
4. S. Tamesue, M. Ohtani, K. Yamada, Y. Ishida, J. M. Spruell, N. A. Lynd, C. J. Hawker, and T. Aida, “Linear
versus dendritic molecular binders for hydrogel network formation with clay nanosheets: studies with ABA
triblock copolyethers carrying guanidinium ion pendants”, J. Am. Chem. Soc., 135, 15650 (2013).
5. Y. Ishida, Y. Matsuoka, Y. Kai, K. Yamada, K. Nakagawa, T. Asahi, and K. Saigo, “Metastable liquid crystal
as time-responsive reaction medium: aging-induced dual enantioselective control”, J. Am. Chem. Soc.,
135, 6407 (2013).
18
Our team aims to create water-based materials,
referred to as aqua materials, as replacements for
conventional plastics. Taking advantage of their unique
properties as moldable, portable water, together with
the elaboration of their inner or surface parts, we will
demonstrate their various applications as intelligent
soft materials. We are employing a wide range of
chemicals as the components of aqua materials, in
order to improve their properties and to ultimately
realize environment-conscious materials. Our
challenge also includes the rational design of novel
bio-inspired materials, by assembling molecules with
dynamic and static functions within aqua materials
used as scaffolds.
Core members
Yoshihiro Yamauchi, Joon-il Cho
(Visiting Scientist) Noriyuki Uchida
(Technical Staff)
Kuniyo Yamada, Noriko Horimoto, Chunji Li
(Student Trainee) Koki Sano, Xiang Wang, Zhifang Sun
Left: Resistance switching of VO2-based EDLT.
Adapted from "Nature 487, 459–462 (2012)." with permission(© 2012 Nature).
Right: Resistance switching of manganite Pr0.5Sr0.5MnO3 -based EDLT.
Hatano, T. et al. Gate control of electronic phases in a quarter-filled manganite. Sci.
Rep. 3, 2904 (2013).
Publications
1. Y. Nii, A. Kikkawa, Y. Taguchi, Y. Tokura, and Y. Iwasa, “Elastic Stiffness of a Skyrmion Crystal”, Phys.
Rev. Lett., 113, 267203 (2014).
2. Y. J. Zhang, T. Oka, R. Suzuki, J. T. Ye, and Y. Iwasa, “Electrically switchable chiral light-emitting
transistor”, Science, 344, 725 (2014).
3. S. Shimizu, K. S. Takahashi, T. Hatano, M. Kawasaki, Y. Tokura, and Y. Iwasa, “Electrically Tunable
Anomalous Hall Effect in Pt Thin Films”, Phys. Rev. Lett., 111, 216803 (2013).
The purpose of our team is to make revolutionary
contribution to the low energy consumption
electronics through creating novel quantum properties
and functions based on devices made by hetero
interfaces between inorganic and organic materials.
The former includes semiconductors, metals, oxides,
and chalcogenides, while the latter includes ionic
liquids, self-assembled monolayers, and conjugated
polymers. In particular, we focus on field effect
emergent phenomena such as electric field induced
superconductivity, Mott transition, electric field
manipulation of spin current, and novel thermoelectric
properties.
Core members
(Research Scientist) Satria Bisri
(Postdoctoral Researcher) Sunao Shimizu
4. T. Hatano, Y. Ogimoto, N. Ogawa, M. Nakano, S. Ono, Y. Tomioka, K. Miyano, Y. Iwasa, and Y. Tokura,
“Gate Control of Electronic Phases in a Quarter-Filled Manganite”, Sci. Rep., 3, 2904 (2013).
5. M. Nakano, K. Shibuya, D. Okuyama, T. Hatano, S. Ono, M. Kawasaki, Y. Iwasa, and Y. Tokura,
“Collective bulk carrier delocalization driven by electrostatic surface charge accumulation”, Nature, 487,
459 (2012).
19
Emergent Soft System Research Team
Emergent Functional Polymers Research Team
Takao Someya (Ph.D.), Team Leader
Keisuke Tajima (Ph.D.), Team Leader
takao.someya@riken.jp
keisuke.tajima@riken.jp
Research field
Research field
Engineering, Chemistry, Materials Sciences
Electronic Engineering, Materials Science
Keywords
Keywords
Organic electronics, Organic field-effect transistor,
Organic light emitting devices, Organic solar cells,
Organic sensors
Organic electronics, Organic solar cells, Polymer
synthesis, Self-assembly, Nanostructure control
Brief resume
Brief resume
2002 Ph.D., The University of Tokyo
1997 Ph.D., Electronic Engineering, University of Tokyo
Imperceptible electronics
that are lighter than a feather
Sensors and electronic circuits for healthcare and medical applications are generally
fabricated using silicon and other rigid electronic materials. To minimize the discomfort of
wearing rigid sensors, it is highly desirable to use soft electronic materials particularly for
devices that come directly into contact with the skin. In this regard, electronics
manufactured on thin polymeric films are very attractive: in general, a thinner substrate will
provide better mechanical flexibility. However, directly manufacturing sensors or electronic
1998 Lecturer, University of Tokyo
2001 JSPS Postdoctoral Fellowship for Research Abroad
(Columbia University)
2011 Project Leader, NEDO project on printed electronics
(-present)
2011 Research Director, JST/ERATO Project (-present)
2015 Chief Scientist, Thin-film deice lab, RIKEN (-present)
2015 Team Leader, Emergent Soft System Research Team,
Supramolecular Chemistry Division, RIKEN CEMS
(-present)
circuits on ultrathin polymeric films with thicknesses of several micrometers or less is a
difficult task if conventional semiconductor processes are used. We have manufactured
the world's thinnest and lightest soft organic transistor integrated circuits (ICs) on ultrathin
polymeric films with a thickness of only 1.2 µm. This was possible because we developed
a novel technique to form a high-quality 19-nm-thick insulating layer on the rough surface
of the 1.2-µm-thick polymeric film. The organic transistor ICs exhibit extraordinary
robustness in spite of being super-thin. Indeed, the electrical properties and mechanical
performance of the transistor ICs were practically unchanged even when squeezed to a
bending radius of 5 µm, dipped in physiological saline, or stretched to up to double their
original size. Finally, these organic transistor ICs have been utilized to develop a flexible
touch sensor system prototype.
Outline
Electronics is expected to support the foundation of
highly develop ICT such as Internet of Things (IoT),
artificial intelligence (AI), and robotics. In addition to
improve the computing speed and storage capacity, it
is required to minimize negative impact of machines
on environment and simultaneously to realize the
harmony between human and machines. We make full
use of the novel soft electronic materials such as novel
organic semiconductors in order to fabricate emergent
thin-film devices and, subsequently, to realize
emergent soft systems that exhibit super-high
efficiency and harmonization with humans. The new
soft systems have excellent features such as
lightweight and large area, which are complimentary to
inorganic semiconductors, are expected to open up
new eco-friendly applications.
2002 Postdoctoral Researcher, Northwestern University
Control of interfacial structures
in organic solar cells
Publications
1. N. Matsuhisa, M. Kaltenbrunner, T. Yokota, H. Jinno, K. Kuribara, T. Sekitani, and T. Someya, “Printable
elastic conductors with a high conductivity for electronic textile applications”, Nat. Commun., 6, 7461 (2015).
2. M. Kaltenbrunner, T. Sekitani, J. Reeder, T. Yokota, K. Kuribara, T. Tokuhara, M. Drack, R. Schwoediauer, I.
Graz, S. Bauer-Gogonea, S. Bauer, and T. Someya, “An ultra-lightweight design for imperceptible plastic
electronics”, Nature, 499, 458 (2013). 3. T. Sekitani, Y. Noguchi, K. Hata, T. Fukushima, T. Aida, and T. Someya, “A rubberlike stretchable active matrix
using elastic conductors”, Science, 321, 1468 (2008).
4. T. Someya, Y. Kato, T. Sekitani, S. Iba, Y. Noguchi, Y. Murase, H. Kawaguchi, and T. Sakurai, “Conformable,
flexible, large-area networks of pressure and thermal sensors with organic transistor active matrixes”, Proc.
Natl Acad. Sci. USA, 102, 12321 (2005).
5. T. Someya, T. Sekitani, S. Iba, Y. Kato, H. Kawaguchi, and T. Sakurai, “A large-area, flexible pressure sensor
matrix with organic field-effect transistors for artificial skin applications”, Proc. Natl Acad. Sci. USA, 101,
9966 (2004).
20
Core members
2009 Lecturer, The University of Tokyo
2011 Associate Professor, The University of Tokyo
- Elucidating the relationship between junction structures
at molecular level and device performances Solution-processed organic solar cells draw much attention as a renewable energy
source since they have unique features such as light-weight, flexibility, and possibility of
2011 PRESTO Researcher, Japan Science and Technology
Agency (-present)
2012 Team Leader, Emergent Functional Polymers Research
Team, RIKEN
2013 Team Leader, Emergent Functional Polymers Research
Team, Supramolecular Chemistry Division, RIKEN Center
for Emergent Matter Science (-present)
low-cost production by using fast coating technologies. This type of devices have
molecular junctions of different materials which generates the current by photoirradiation,
thus the nature of the organic interfaces affects their performance significantly. However,
Outline
it is difficult to analyze the interfacial structures in the films prepared by the conventional
methodology relying on the mixture of the materials, and there have been no mean to
modify the structures at those complicated interfaces. These difficulties hinder pursuing
the ideal interfacial structure to improve the performance.
Our team has been studying
on the relationship between the junction structures at molecular level and the
performance of the solar cells based on a unique methodology: lamination of two organic
films. We recently found that either introduction of a thin layer of an insulating material at
the interface and doping of the layer with small amount of an organic dye or an energy
“cascade” structure at the interface introduced by using surface segregated monolayers
could avoid the trade-off relationship between the photocurrent and the photovoltage,
resulting in the increase of the performance. These findings could lead to a breakthrough
for the further enhancement of the performance in organic solar cells.
S
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S
Exciton
diffusion
S
S
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S
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S
Exciton
diffusion
S
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O
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S
Rf
O
O
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Rf
O
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Rf
O
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Energy
cascade
O
O
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O
O
O
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O
O
O
O
CT state
O
O
O
S
Rf
Rf
O
O
Insulator
䠇
Organic
dye
S
S
S
CT state
O
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CT state
O
(Research Scientist) Kenjiro Fukuda
S
S
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O
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O
O
S
S
S
S
Energy
transfer
Organic dye
(Left) E-skins with organic thin-film devices
developed in 2003 were applied on a robotic
hand. (Right) Ultraflexible organic integrated
circuits manufactured on a 1 μm-thick plastic
film were applied on a human hand.
2004 Research Associate, The University of Tokyo
O
O
O
O
O
O
O
O
O
O
O
O
O
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O
O
O
Schematic representation of the structures of donor/acceptor interface and photophysical
processes without interlayer (center), with the insulating layer and the organic dye molecules (left),
and with the energy cascade structure by using the surface segregated monolayer (right).
Publications
1. S. Izawa, K. Nakano, K. Suzuki, K. Hashimoto, and K. Tajima, “Dominant Effects of First Monolayer
Energetics at Donor/Acceptor Interfaces on Organic Photovoltaics”, Adv. Mater., 27, 3025 (2015).
2. Y. F. Zhong, A. Tada, S. Izawa, K. Hashimoto, and K. Tajima, “Enhancement of VOC without Loss of JSC in
Organic Solar Cells by Modification of Donor/Acceptor Interfaces”, Adv. Energy Mater., 4, 1301332 (2014).
We w o r k o n t h e d e v e l o p m e n t o f n e w o r g a n i c
semiconducting polymer materials and their
application to organic electronic devices. Specifically,
relying on the basic chemistry of the intermolecular
interactions during the film forming process from the
solutions, we seek the methodology and the molecular
design to control the precise structures in moleculara n d n a n o - s c a l e a t o u r w i l l , a n d t r y t o fi n d
breakthroughs to drastically enhance the performance
of the organic electronic devices. Targets of our
research are not only the conventional organic solar
cells and field-effect transistors, but also the organic
electronic devices with new functions based on the
structure controls.
Core members
(Postdoctoral Researcher) Kyohei Nakano,
Jianming Huang, Soo Won Heo, Chao Wang
(Visiting Researcher) Seiichiro Izawa
(Technical Staff) Kaori Suzuki
3. J. S. Ma, K. Hashimoto, T. Koganezawa, and K. Tajima, “Enhanced Vertical Carrier Mobility in Poly
(3-alkylthiophene) Thin Films Sandwiched with Self-assembled Monolayer and Surface-segregated
Layer”, Chem. Commun., 50, 3627 (2014).
4. E. J. Zhou, J. Z. Cong, K. Hashimoto, and K. Tajima, “Control of Miscibility and Aggregation via Material
Design and Coating Process for High-Performance Polymer Blend Solar Cell”, Adv. Mater., 25, 6991 (2013).
5. J. S. Ma, K. Hashimoto, T. Koganezawa, and K. Tajima, “End-On Orientation of Semiconducting
Polymers in Thin Films Induced by Surface Segregation of Fluoroalkyl Chains”, J. Am. Chem. Soc.,135,
9644 (2013).
21
Emergent Bioengineering Materials
Research Team
Materials Characterization Support Unit
Yoshihiro Ito (D.Eng), Team Leader
Daisuke Hashizume (D.Sci), Unit Leader
y-ito@riken.jp
hashi@riken.jp
Research field
Research field
Structural Chemistry, Materials Science,
Analytical Chemistry
Materials Sciences, Bioengineering, Organic Chemistry
Keywords
Keywords
Energy conversion, Sensors, Precise Polymer
Synthesis, Molecular evolutionary engineering,
Nanobiotechnology
X-ray crystal structure analysis, Electron microscopy,
Chemical analysis
Brief resume
Brief resume
1987 D.Eng., Kyoto University
An aqueous process to disperse carbon
nanotube for preparation of composite materials
Single-walled carbon nanotubes (SWCNTs) have received a great deal of attention in
the past two decades; their extreme mechanical strength and thermal, kinetic, and electrical properties are of great interest for carbon-based devices. However, SWCNTs form
bundles owing to van der Waals interactions and result in poor solubility; applications in
water are very limited. Peptides are regarded as promising noncovalent dispersants for
SWCNTs in water, because the peptide backbone forms a helical conformation stabilized
by hydrogen bonds. We found that the peptide aptamer, which was selected by the ribo-
1988 Assistant Professor, Kyoto University
1996 Associate Professor, Kyoto University
1997 Associate Professor, Nara Institute of Science and
Technology
1999 Professor, University of Tokushima
2001 Project Leader, Kanagawa Academy of Science and
Technology
2004 Chief Scientist, Nano Medical Engineering Laboratory,
RIKEN (-present)
2013 Team Leader, Emergent Bioengineering Materials
Science (-present)
Outline
1997 Tokyo Institute of Technology, PhD in Chemistry
Visualization of chemical bonds by
accurate X-ray analysis
Our unit has investigated nature of molecules, which have unusual chemical bonds and
show less stability, in the crystalline state by analyzing distribution of valence electrons
derived from accurate and precise single crystal X-ray crystal structure analysis.
Conventional X-ray diffraction method clarifies arrangement of atoms in the crystalline
state by modeling total electron density distribution using spherical atom (isolated atom)
models. As widely recognized, the resulted structures give important information on the
analyzed. In this study, the valence densities are analyzed by applying multipole models
uate the effective dispersion capability of the peptide aptamer, isothermal titration calorim-
instead of the spherical atom models to gain much direct information on the electronic
etry was used to estimate binding enthalpies in water. The ΔH value of the aptamer was 3
structure of molecules.
and 5 times higher than those of the low-molecular-weight surfactant and the computationally designed peptides, respectively. Molecular dynamics simulations showed that π−π
semiconducting SWCNTs using a uniform density gradient ultracentrifuge. This method enabled
aqueous process to disperse carbon nanotube
for preparation of composite materials.
Representative conformation of the peptide aptamer
on a SWCNT. (a) Side view and (b) front view.
Reprinted with permission from Li, Z. et al. Langmuir 2015,
31, 3482-3488. Copyright 2015 American Chemical Society.
Publications
1. Z. Li, T. Kameda, T. Isoshima, E. Kobatake, T. Tanaka, Y. Ito, and M. Kawamoto, “Solubilization of
Single-Walled Carbon Nanotubes using a Peptide Aptamer in Water below Critical Micelle Concentration”,
Langmuir, 31, 3482 (2015).
2. Y. Manandhar, T. Bahadur K.C., W. Wang, T. Uzawa, T. Aigaki, and Y. Ito, “In vitro selection of a peptide
aptamer that changes fluorescence in response to verotoxin”, Biotechnol. Lett., 37, 619 (2015).
3. S. Tada, Q. Zang, W. Wang, M. Kawamoto, M. Liu, M. Iwashita, T. Uzawa, D. Kiga, M. Yamamura, and Y.
Ito, “In vitro selection of a photoresponsive peptide aptamer to glutathione-immobilized microbeads”, J.
Biosci. Bioeng., 119, 137 (2015).
4. W. Wang, T. Uzawa, N. Tochio, J. Hamatsu, Y. Hirano, S. Tada, H. Saneyoshi, T. Kigawa, N. Hayashi, Y. Ito,
M. Taiji, T. Aigaki, and Y. Ito, “A fluorogenic peptide probe developed by in vitro selection using tRNA
carrying a fluorogenic amino acid”, Chem Commun., 50, 2962 (2014).
5. P. M. Sivakumar, N. Moritsugu, S. Obuse, T. Isoshima, H. Tashiro, and Y. Ito, “Novel microarrays for
simultaneous serodiagnosis of multiple antiviral antibodies”, PLoS ONE, 8, e81726 (2013).
22
Outline
separation, bonding mode and intermolecular interaction, the valence densities should be
persed SWCNTs are clearly observed using the peptide aptamer below the CMC. To eval-
sibility of diameter-dependent separation of
2013 Unit Leader, Materials Characterization Support Unit,
Supramolecular Chemistry Division, RIKEN Center for
the nature and chemistry of the analyzed molecule, in particular, reactivity, charge
(TEM) image also revealed insoluble SWCNTs form large bundles. In contrast, well-dis-
strength. The peptide aptamer showed the pos-
2011 Senior Research Scientist, Materials Characterization
Team, Advanced Technology Support Division, RIKEN
chemistry of molecule, is not included in the resulted models. For deeply understanding
tion (CMC) at a low concentration of 0.02 w/v%. The transmission electron microscopic
important role in imparting a high binding
2002 Research Scientist, Molecular Characterization Team,
Advanced Development and Support Center, RIKEN
nature of molecules. However, valence density distribution, which plays critical roles in
some display, had the highest dispersion capability below the critical micelle concentra-
interactions between aromatic units of amino acids and the side walls of SWCNTs play an
1997 Research Associate, Department of Applied Physics and
Chemistry, Univ. of Electro-Communications
Advanced materials composed of biological and
artificial components are synthesized for development
of environmentally friendly energy collection and
conversion systems. By combination of organic
synthetic chemistry, polymer chemistry, and
biotechnology, novel synthesis method will be
established and materials using biological and artificial
elements will be achieved by their chemical
fabrication, and the characterization of the interfaces
between biological and artificial elements for highly
efficient energy collection and conversion. Especially
our team will establish a new methodology, a
chemically extended molecular evolutionary
engineering as an “Emergent Chemistry” to create a
specific ally functionalized polymer by screening of
random sequence of polymer library containing
functional monomers.
Core members
Masuki Kawamoto, Takanori Uzawa
(Research Scientist) Motoki Ueda
(Company-Sponsored Researcher) Kenta Tanaka
(Junior Research Associate) Krishnachary Salikolimi,
Tara KC Bahadur, Fathy Hassan, Yun Heo
(Technical Staff) Noriko Minagawa, Izumi Kono
Electron donation from σ (C−C) orbital to Si atom visualized by accurate X-ray analysis.
Publications
1. S. Ito, Y. Ueta, T. T. T. Ngo, M. Kobayashi, D. Hashizume, J. Nishida, Y.Yamashita, and K. Mikami, “Direct
arylations for study of the air-stable P-heterocyclic biradical: From wide electronic tuning to
characterization of the localized radicalic electrons”, J. Am. Chem. Soc., 135, 17610 (2013).
2. R. Rodriguez, T. Troadec, D. Gau, N. Saffon-Merceron, D. Hashizume, K. Miqueu, J.-M. Sotiropoulos,
A.Baceiredo, and T. Kato, “Synthesis of a donor-stabilized silacyclopropan-1-one”, Angew. Chem. Int.
Ed., 52, 4426 (2013).
Our unit provides research support by means of X-ray
crystal structure analysis, electron microscopy, and
elemental analysis. In addition to supporting on the
individual method, we propose multifaceted research
support by combining these methods. To keep our
support at the highest level quality, we always update
our knowledge and make training in our skills. We
make tight and deep collaboration with researchers to
achieve their scientific purposes and to propose new
insights into the research from analytical point of view,
in addition to providing routinely analysis. Furthermore,
we challenge to develop unexplored measurement
methods directed to more advanced and
sophisticated analysis.
Core members
(Special Temporary Employee) Chieko Kariya
(Senior Technical Scientist) Keiko Suzuki
(Technical Scientist) Daishi Inoue
(Technical Staff) Tomoka Kikitsu, Yoshio Maebashi
3. L. Li, T. Fukawa, T. Matsuo, D. Hashizume, H. Fueno, K. Tanaka, and K. Tamao, “A stable germanone
as the first isolated heavy ketone with a terminal oxygen atom”, Nat. Chem., 4, 361 (2012).
4. K. Suzuki, T. Matsuo, D. Hashizume, H. Fueno, K. Tanaka, and K. Tamao, “A planar rhombic
charge-separated tetrasilacyclobutadiene”, Science, 331, 1306 (2011).
5. E. Ohta, H. Sato, S. Ando, A. Kosaka, T. Fukushima, D. Hashizume, M. Yamasaki, K. Hasegawa, A.
Muraoka, H. Ushiyama, K. Yamashita, and T. Aida, “Redox-responsive molecular helices with highly
condensed π-clouds”, Nat. Chem., 3, 68 (2010).
23
Quantum Information Electronics Division
Quantum Functional System Research Group
Quantum Condensed Matter Research Group
Seigo Tarucha (Dr.Eng.), Group Director
Franco Nori (Ph.D.), Group Director
tarucha@riken.jp
fnori@riken.jp
Research field
Research field
Physics, Engineering, Materials Sciences,
Computer Science, Biology, Multidisciplinary
Physics, Engineering
Keywords
Keywords
Quantum computing, Quantum simulation, Quantum
relay, Spin control, Quantum dots, Nanodevices
Condensed matter physics, Atomic physics, Quantum
optics, Artificial atoms, Superconducting qubits,
Quantum information processing
Brief resume
1978 Staff member at the Basic Research Laboratories of
Nippon Tel. & Tel. Corp.
Brief resume
1986 Visiting Scientist , MPI (Stuttgart, Germany)(-1987)
Non-destructive detection of spin
in a double quantum dot
The transfer of quantum information between single photons and solid-state quanta such
as charge and spin has been extensively studied towards the establishment of a global
quantum information network. Here we have realized the nondestructive single
photoelectron spin detection using quantum dot (QD) toward such information transfer
between photons and electron spins.
We used a gate defined lateral double QD (DQD) embedded in two-dimensional electron
gas with a charge sensor (quantum point contact) and a metal mask fabricated on the
surface above the DQD (Fig. 1). The key issue is the use of the inter-dot resonant tunneling
between two QDs in order to raise the fidelity of single electron detection. The resonant
1993 Distinguished member of technical staff, NTT Basic
Research Laboratories (-1998)
1995 Visiting Professor , Delft University of Technology (Delft,
The Netherlands)
1990 Leader, Research Program on Electron Transport in
Low-Dimensional Semiconductor Structures, NTT Basic
Research Laboratories(-1998)
Tokyo (-present)
Interdisciplinary theoretical investigations in
atomic physics, quantum optics, and
condensed matter physics, applied to
quantum nano-electronics
Our group has obtained various new research results doing interdisciplinary theoretical
2012 Visiting Professor, Institut Néel CNRS, université Joseph
Fourier(France)
and computational investigations in atomic physics, quantum optics, and condensed
2013 Group Director, Quantum Functional System Research
Group, Division Director, Quantum Information
Electronics Division, RIKEN Center for Emergent Matter
Science (-present)
uncovered new phenomena in semi- and super-conducting electrical devices, behaving
Outline
matter physics, in the context of engineered quantum nano-electronics. We have
1987 Ph.D., University of Illinois at Urbana-Champaign, USA
1987 Research Fellow, University of California, Santa Barbara,
USA
1990 Assistant, 1996, Associate, 2004, Full Professor,
University of Michigan, USA
2001 Team Leader, Digital Materials Team, Frontier Research
System and Advanced Science Institute, RIKEN
2013 Group Director, Quantum Condensed Matter Research
Group, Quantum Information Electronics Division, RIKEN
Outline
as artificial atoms, which provide an unprecedented platform for experimentally realizing
controlled and designable quantum systems. These devices allow the creation of circuit
analogues and simulations of quantum phenomena from a wide range of fields of physics
tunneling event gives distinct evidence of trapping of single photoelectrons and it is
and chemistry. We also pioneered the study of electron vortex beams and other
detected by observing the oscillating current in the charge sensor. Such signals are clearly
optics-like phenomena. Interdisciplinary research on this type (often in collaboration with
observed when a single photoelectron is captured after pulsed photon irradiation (Fig. 2).
experimentalists) will continue catalyzing discoveries and make new connections between
We have also achieved the spin state detection of photoelectrons using our DQD with
various subfields of physics.
spin-blockade effect based on Pauli exclusion. The suppression in resonant tunneling signal
is observed when the spin of the photoelectron is in parallel with that of the other electron
trapped beforehand. Now we continue the improvement of the fidelity to detect the
superposition state of single photon toward the realization of quantum information network.
(Fig. 1) Schematic diagram of our device structure. (Fig.2) Measured single photon detection
signal in experiment. A fluctuation in the current is seen when a single extra charge tunnels
between the two dots until the electron escapes from the dot.
Publications
1. J. Yoneda, T. Otsuka, T. Nakajima, T. Takakura, T. Obata, M. Pioro-Ladrière, H. Lu, C. J. Palmstrøm, A. C.
Gossard, and S. Tarucha, “Fast Electrical Control of Single Electron Spins in Quantum Dots with Vanishing
Influence from Nuclear Spins”, Phys. Rev. Lett., 113, 267601 (2014).
2. M. R. Delbecq, T. Nakajima, T. Otsuka, S. Amaha, J. D. Watson, M. J. Manfra, and S. Tarucha, “Full control
of quadruple quantum dot circuit charge states in the single electron regime”, Appl. Phys. Lett., 104,
183111 (2014).
3. T. Otsuka, Y. Sugihara, J. Yoneda, T. Nakajima, and S. Tarucha, “Measurement of Energy Relaxation in
Quantum Hall Edge States Utilizing Quantum Point Contacts”, J. Phys. Soc. Jpn., 83, 014710 (2014).
4. S. Amaha, W. Izumida, T. Hatano, S. Tarucha, K. Kono, and K. Ono, “Spin blockade in a double quantum
dot containing three electrons”, Phys. Rev. B, 89, 085302 (2014).
5. T. Fujita, H. Kiyama, K. Morimoto, S. Teraoka, G. Allison, A. Ludwig, A. D. Wieck, A. Oiwa, and S. Tarucha,
“Nondestructive Real-Time Measurement of Charge and Spin Dynamics of Photoelectrons in a Double
Quantum Dot”, Phys. Rev. Lett., 110, 266803 (2013).
24
We study hardware and underlying physics for quantum
information processing with quantum control of soli-state
quantum states. Quantum information processing is an
ideal information technology whose operation
accompanies low-energy dissipation and high information
security. The purpose of our group is to demonstrate the
ability of the solid-state information processing using
q u a n t u m o p e r a t i o n s o f q u a n t u m c o h e re n c e a n d
entanglement in semiconductor and superconductor
nanostructures and finally outline a path for the realization.
The specific research targets are "quantum computing"
including quantum logic operation and quantum
simulation, "quantum interface" which can offer quantum
memory and relay, and "quantum nanodevices" relevant
for the quantum control. We investigate architectures for
best suited quantum systems, science and technology for
both materials and devices, and fundamental physics of
quantum entanglement decoherence and spin correlation.
Core members
(Research Scientist) Shinichi Amaha, Giles Allison,
Michael Desmond Fraser
(Postdoctoral Researcher) Takashi Nakajima, Tomohiro
Otsuka, Matthieu Romain Delbecq, Kenta Takeda
(Special Postdoctoral Researcher)
Jun Yoneda, Hiroshi Kamata
(Junior Research Associate)
Marian Nicola Joachim Marx
(Student Trainee) Akito Noiri, Takumu Honda,
Takumi Ito, Kento Kawasaki, Yasuhiro Matsuo
Top part of the figure: a fast-oscillating mirror produces quantum-correlated photon pairs.
Bottom part of the figure: a dc SQUID with a very fast oscillating applied magnetic flux
mimics the very fast-oscillating mirror.
(PRL 2009, PRA 2010, Nature, 2011, PRA 2013).
Publications
1. I. Georgescu, S. Ashhab, and F. Nori, “Quantum Simulation”, Rev. Mod. Phys., 86, 153 (2014).
We perform research in theoretical condensed matter
physics, atomic physics, quantum information,
computational physics, transport phenomena, energy
conversion and solar energy. Our research work is
interdisciplinary and also explores the interface
between atomic physics, quantum optics,
nano-science, and computing. We are also studying
s u p e rc o n d u c t i n g J o s e p h s o n - j u n c t i o n q u b i t s ,
nano-mechanics, hybrid quantum electro-mechanical
systems, quantum nano-electronics, quantum
emulators, artificial photosynthesis, and light - to electricity conversion. An underlying theme of our
work is to better understand nano-scale quantum
systems and devise methods to control them. We use
physical models to make predictions that can be
tested experimentally and that can be used to better
understand the observed phenomena.
2. B. Peng, et al., “Parity-time-symmetric whispering-gallery microcavities”, Nat. Phys., 10, 394-398 (2014).
3. B. Peng, et al., “Loss-induced suppression and revival of lasing”, Science, 346, 328-332 (2014).
4. K. Y. Bliokh, Y. S. Kivshar, and F. Nori, “Magnetoelectric Effects in Local Light-Matter Interactions”,
Phys. Rev. Lett., 113, 033601 (2014).
5. Z.-L. Xiang, S. Ashhab, J.Q. You, and F. Nori, “Hybrid quantum circuits: Superconducting circuits
interacting with other quantum systems”, Rev. Mod. Phys., 85, 623 (2013).
6. J.Q. You, and F. Nori, “Atomic physics and quantum optics using superconducting circuits”, Nature,
474, 589 (2011)
Core members
(Research Scientist) Konstantin Bliokh, Neill Lambert
(Postdoctoral Researcher) Anton Frisk Kockum
(Visiting Researcher) Peng Zhang
(Visiting Scientist) Natsuko Ishida
7. C. M. Wilson, et al. “Observation of the dynamical Casimir effect in a superconducting circuit”, Nature,
479, 376 (2011). Physics World top five Breakthroughs of the Year 2011. Also, the top Readers' choice
of 2011 on Nature News.
25
Quantum Condensate Research Team
Superconducting Quantum Electronics
Research Team
Masahito Ueda (Ph.D.), Team Leader
Yasunobu Nakamura (D.Eng.), Team Leader
masahito.ueda@riken.jp
yasunobu.nakamura@riken.jp
Research field
Research field
Physics/Engineering/Quantum information science
Quantum Information Science
Keywords
Keywords
Ultracold atoms, Bose-Einstein condensates, Optical
lattice, Quantum simulation, Quantum correlations
Superconductivity, Microwave, Quantum information,
Quantum optics, Quantum correlations
Brief resume
Brief resume
1992 Researcher, Fundamental Research Laboratories, NEC
Corporation
1988 Resercher, NTT Basic Research Laboratories
Topological excitations
in Bose-Einstein condensates
Bose-Einstein condensates offer a cornucopia of symmetry breaking because a rich
1994 Associate Professor, Hiroshima University
2000 Professor, Tokyo Institute of Technology
2014 Team Leader, Quantum Condensate Research Team,
Quantum Information Electronics Division, RIKEN Center
Microwave quantum optics
in superconducting circuits
There is almost no energy dissipation in superconducting electrical circuits. Therefore,
variety of internal degrees of freedom are available depending on the atomic species. We
alternating current flows in a microwave resonator for a long period of time, and
have used these degrees of freedom to explore various aspects of symmetry breaking
microwave signal travels along a transmission line without damping. Quantum
and topological excitations. Among them are the so-called Kibble-Zurek mechanism in
Outline
mechanically, these can be described as storage and transmission of microwave
which the order parameter develops singularities after some parameter of the system is
‘photons’ confined in the circuits. Similarly, superconducting quantum-bit (qubit) circuits
suddenly quenched. Ordinary vortices and spin vortices are found to emerge. We also
consist of elements such as capacitors and inductors. However, due to strong
investigate novel topological phenomena such as knot excitations in an antiferromagnetic
nonlinearity induced by a Josephson junction, an additional inductive element, they can
Bose-Einstein condensate.
store at most a single quantum of microwave.
We combine those components, i.e., qubits, resonators, and transmission lines, for
manipulation of quantum states of the microwave modes. Differently from the case in free
1997 Senior Researcher, Fundamental Research Laboratories,
NEC Corporation
2001 Principal Researcher, Fundamental Research
Laboratories, NEC Corporation
2001 Visiting Scientist, Delft University of Technology, The
Netherlands (-2002)
2002 Frontier Researcher, Frontier Research Systems, RIKEN
2005 Research Fellow, Fundamental and Environmental
Research Laboratories, NEC Corporation
2008 Visiting Researcher, Advanced Science Institute, RIKEN
2012 Professor, Department of Applied Physics, The
University of Tokyo
2012 Professor, Research Center for Advanced Science and
Technology, The University of Tokyo (-present)
2014 Team Leader, Superconducting Quantum Electronics
Science (-present)
Outline
space, electromagnetic field in the circuits is confined effectively either in 0-dimension
(qubit and resonator) and 1-dimension (transmission line), allowing efficient generation
We aim to explore physics frontiers at the that lie at
the boarderlines between quantum physics, measurement, information and thermodynamics. In particular,
we explore novel phenomena in ultracold atoms which
offer a versatile tool to investigate universal quantum
phenomena that are independent of material-specific
parameters.
and detection of single photons and other nonclassical states of microwave. We have
proposed and demonstrated a quantum node consisting of a driven superconducting
qubit, which works as a frequency down-converter of a single microwave photon, for
example.
Core members
(Research Scientist) Naoto Tsuji
Tomoya Hayata, Shun Uchino
Ground-state phase diagram of a spin-2 Bose-Einstein condensate (BEC).
Depending on the phase, different topological excitations appear.
Frequency down-conversion with a Λ-type three-level system using a driven
superconducting quantum bit. Left: Schematics and an energy-level diagram. Right:
Micrographs of the device.
Publications
Publications
1. Y. Horinouchi, and M. Ueda, “Onset of a Limit Cycle and Universal Three-Body Parameter in Efimov
Physics”, Phys. Rev. Lett., 114, 025301 (2015).
2. N. T. Phuc, Y. Kawaguchi, and M. Ueda, “Quantum Mass Acquisition in Spinor Bose-Einstein
Condensates”, Phys. Rev. Lett., 113, 230401 (2014).
2. Z. R. Lin, K. Inomata, K. Koshino, W. D. Oliver, Y. Nakamura, J. S. Tsai, and T. Yamamoto, “Josephson
parametric phase-locked oscillator and its application to dispersive readout of superconducting
qubits”, Nat. Commun., 5, 4480 (2014).
3. M. Ueda, “Topological aspects in spinor Bose-Einstein condensates” (Key Issues Review) Rep. Prog.
Phys., 77, 122401 (2014).
3. K. Koshino, K. Inomata, T. Yamamoto, and Y. Nakamura, “Implementation of an impedance-matched Λ
system by dressed-state engineering”, Phys. Rev. Lett., 111, 153601 (2013).
4. P. Naidon, S. Endo, and M. Ueda, “Microscopic Origin and Universality Classes of the Efimov Three-Body
Parameter”, Phys. Rev. Lett., 112, 105301 (2014).
4. Z. R. Lin, K. Inomata, W. D. Oliver, K. Koshino, Y. Nakamura, J. S. Tsai, and T. Yamamoto, “Single-shot
readout of a superconducting flux qubit with a flux-driven Josephson parametric amplifier”, Appl. Phys.
Lett., 103, 132602 (2013).
5. D. M. Stamper-Kurn and, M. Ueda, “Spinor Bose gases: Symmetries, magnetism, and quantum
dynamics”, Rev. Mod. Phys., 85, 1191 (2013).
26
1. K. Inomata, K. Koshino, Z. R. Lin, W. D. Oliver, J. S. Tsai, Y. Nakamura, and T. Yamamoto, “Microwave
down-conversion with an impedance-matched Λ system in driven circuit QED”, Phys. Rev. Lett., 113,
063604 (2014).
We study quantum information electronics using
artificial quantum systems based on superconducting
circuits. Superconducting quantum bits are realized in
Josephson-junction circuits and utilized as an
elementary component for quantum information
processing as well as a basic tool for quantum state
control and measurement. Qubits are coupled with
superconducting
microwave
resonators
and
transmission lines, enabling quantum state control of
the microwave modes. Quantum optical technologies
in the microwave domain will be developed and applied
to quantum information science.
Core members
(Senior Research Scientist) Hiroki Ikegami
(Research Scientist) Kunihiro Inomata
(Foreign Postdoctoral Researcher) Lin Zhirong
(Special Postdoctoral Researcher) Hiroyasu Tajima
(Technical Staff) Koichi Kusuyama
5. K. Koshino, S. Ishizaka, and Y. Nakamura, “Deterministic photon-photon √SWAP gate using a Λ
system”, Phys. Rev. A, 82, 010301(R) (2010).
27
Emergent Phenomena Observation
Technology Research Team
Quantum Nano-Scale Magnetism
Research Team
Daisuke Shindo (D.Eng), Team Leader
Yoshichika Otani (D.Sci.), Team Leader
daisuke.shindo@riken.jp
yotani@riken.jp
Research field
Research field
Materials Sciences, Physics, Engineering
Keywords
Keywords
Nanomagnetism, Spintronics, Spin accumulation,
Spin current, Spin Hall effect
Imaging, Electron microscopy, Flux quantum,
Electron holography, Nanomagnetism
Brief resume
Collective motion of electrons visualized
by electron holography
Comprehensive understanding of electromagnetic fields requires their visualization both
inside and outside materials. Since electromagnetic fields originate from various motions
of electrons, comprehensive study of motions of electrons is of vital importance as well as
of significant interest for understanding various emergent phenomena. The purpose of
this study is to extend electron holography technology to visualize motions of electrons.
By detecting electric field variations through amplitude reconstruction processes for
holograms, we have succeeded in visualizing collective motions of electrons. Figure 1
shows one of our experimental results of visualization of the collective motions of
electrons by electron holography using an insulating biomaterial (microfibrils of sciatic
Brief resume
1982 D. Eng., Tohoku University
1989 D.Sci.,Department of Physics, Keio University
1982 Research Associate, Institute for Materials Research at
Tohoku University
1989 Research Fellow, Trinity College University of Dublin,
Ireland
1992 Associate Professor, Institute for Advanced Materials
Processing at Tohoku University
1994 Professor, Institute of Multidisciplinary Research for
Advanced Materials at Tohoku University (-present)
2010 Visiting Scientist, Quantum Phenomena Observation
Technology Team, RIKEN
2012 Quantum Phenomena Observation Technology Team,
RIKEN
2012 Team Leader, Emergent Phenomena Observation
Technology Research Team, RIKEN
2013 Team Leader, Emergent Phenomena Observation
Technology Research Team, Quantum Information
Electronics Division, RIKEN Center for Emergent Matter
Science (-present)
Outline
nerve tissue) specimen with two branches. In the reconstructed amplitude images, the
Development of spintronic
devices based on pure spin currents
- Successful long distance transmission of collective spin precession Modern electronic devices are based on the fundamental concept of electrical charges
moving through a circuit. There are, however, alternative schemes that promise faster and
more efficient computing. An example is spintronics, which exploits the electrons’
magnetic properties, their spins, as well as their electronic charges. Our team has
developed spin information transfer in nonmagnetic metals. When the magnetic field is
applied perpendicular to the spin orientation, a collective spin precession is induced by its
torque. The spin precession signal is detected by means of electrical methods. In the
experiments, the spin current can even be detected after 10µm because of our efficient
current-based memory and logic devices.
electrons can be detected through electric
field variation and can be visualized through
3. D. Shindo, S. Aizawa, Z. Akase, T. Tanigaki, Y. Murakami and H. S. Park, “Electron holographic visualization
of collective motion of electrons through electric field variation”, Microscopy and Microanalysis, 20,
1015-1021 (2014).
4. T. Tanigaki, K. Sato, Z.Akase, S. Aizawa, H. S. Park, T. Matsuda, Y. Murakami, D. Shindo and H. Kawase,
“Split-illumination electron holography for improved evaluation of electrostatic potential associated with
electrophotography”, Appl. Phys. Lett., 104, 131601 (2014).
5. T. Tanigaki, S. Aizawa, H. S. Park, T. Matsuda, K. Harada and D. Shindo, “Advanced split-illumination
electron holography without Fresnel fringes”, Ultramicroscopy, 137, 7-11 (2014).
28
Outline
behavior that is independent of the material used. This will be beneficial for designing spin
results indicate that the collective motions of
2. Y. Murakami, K. Niitsu, T. Tanigaki, R. Kainuma, H. S. Park, and D. Shindo, “Magnetization amplified by
structural disorder within nanometre-scale interface region”, Nat. Commun., 5, 4133 (2014).
2013 Team Leader, Quantum Nano-Scale Magnetism
Research Team, Quantum Information Electronics
Division, RIKEN Center for Emergent Matter Science
(-present)
coherence of the spin precession as a function of the travel distance shows a universal
indicated by arrows in Fig. 1(b) and (c). These
1. H. S. Park, Z. Yu, S. Aizawa, T. Tanigaki, T. Akashi, Y. Takahashi, T. Matsuda, N. Kanazawa, Y. Onose, D.
Shindo, A. Tonomura, and Y. Tokura, “Observation of the magnetic flux and three-dimensional structure of
skyrmion lattices by electron holography”, Nat. Nanotechnol., 9, 337-342 (2014).
2004 Professor, ISSP University of Tokyo (-present)
is enhanced by uniformized velocity of the individual electron spins. Moreover, the
localized and the position of the region changes gradually between the two branches as
Publications
2001 Team Leader, Quantum Nano-Scale Magnetics Team,
RIKEN
as travel distances increase. This is due to the fact that the coherence in spin precession
prominent. When the amount of electron irradiation is increased, however, red regions are
Binarized reconstructed-amplitude
images (red and white) around
microfibrils of sciatic nerve tissue
(blue). The red regions indicate the
area where electric field fluctuates
due to motions of electrons.
1995 Associate Professor, Tohoku University
decrease, the quality of the collective spin precession, the so-called coherence, improves
electrons. At the initial state (Fig. 1(a)), the electric field variations indicated by red are not
holograms.
1992 Research Instructor, Keio University
spin injection technique. Even though the absolute magnitude of the spin signal may
red regions indicate the area where electric field fluctuates due to the motions of
a m p l i t u d e re c o n s t r u c t i o n p ro c e s s f o r
1991 Postdoctoral Researcher, Laboratoire Louis Néel, CNRS,
France
For the purpose of observation and analysis of
emergent phenomena, our team carries out advanced
electron microscopy, especially electron holography.
Electron holography is a leading-edge observation
technology which utilizes the interference effect of the
electron wave and can visualize electromagnetic fields
on the nanometer scale. By developing multifunctional
TEM-specimen holders equipped with plural probes,
changes of the electromagnetic fields of a specimen
under the voltage and applied magnetic field are
quantitatively investigated. By improving the resolution
and precision of these observation technologies, we
can extensively study the mechanism of emergent
phenomena in newly designed specimens of
many-body systems with multiple degrees of freedom.
Core members
(Senior Research Scientist) Ken Harada
(Postdoctoral Researcher) Kodai Niitsu
(Technical Staff) Keiko Shimada
SEM image of a lateral spin valve
used for observing collective spin
precession. The external magnetic
fi e l d B i n d u c e s c o l l e c t i v e s p i n
precession indicated red arrows over
a long distance 10µm.
Publications
1. H. Idzuchi, Y. Fukuma, and Y. Otani, “Spin transport in non-magnetic nano-structures induced by
non-local spin injection”, Physica E, 68, 239 (2015).
2. H. Idzuchi, Y. Fukuma, S. Takahashi, S. Maekawa, and Y. Otani, “Effect of anisotropic spin absorption
on the Hanle effect in lateral spin valves”, Phys. Rev. B, 89, 081308(R) (2014).
3. Y. Niimi, H. Suzuki, Y. Kawanishi, Y. Omori, T. Valet, A. Fert, and Y. Otani, “Extrinsic spin Hall effects
measured with lateral spin valve structures”, Phys. Rev. B, 89, 054401 (2014).
4. T. Wakamura, N. Hasegawa, K. Ohnishi, Y. Niimi, and Y. Otani, “Spin injection into a superconductor
with strong spin-orbit coupling, Phys. Rev. Lett., 112, 036602 (2014).
In Quantum Nano-Scale Magnetism Team, we fabricate nano-scale magnetic tunnel junctions and ferromagnetic/nonmagnetic hybrid nano-structures
consisting of metals, semiconductors, and insulators
to study quantum behaviors in domain wall displacement and magnetization dynamics mediated by spin
current, i.e. a flow of spin angular momentum. In
particular, we focus our investigation on the fundamental process of spin angular momentum conversion
between quasi-particles such as electron spin,
magnon and phonon to improve the efficiency to
generate the spin current. We also aim at developing a
new technique to control the spin conversion by using
underlying exchange and spin-orbit interactions, and
develop a new class of low power spintronic devices
for innovative energy harvesting.
Core members
Kouta Kondou, Bivas Rana, Junyeon Kim,
Jorge Luis Puebla Nunez
(Junior Research Associate) Norinobu Hasegawa
(Student Trainee) Shutarou Karube
5. Y. Niimi, D. H. Wei, H. Idzuchi, T. Wakamura, T. Kato, and Y. Otani, ”Experimental verification of
comparability between spin-orbit and spin-diffusion lengths”, Phys. Rev. Lett., 110, 016805 (2013).
29
Quantum System Theory Research Team
Spin Physics Theory Research Team
Daniel Loss (Ph.D.), Team Leader
Gen Tatara (D.Sci), Team Leader
loss.daniel@riken.jp
gen.tatara@riken.jp
Research field
Research field
Theoretical Physics,
Quantum Theory of Condensed Matter
Keywords
Keywords
Spintronics, Spin-orbit interaction, Domain wall,
Monopole, Spin current, Metamaterial
Quantum dots, Spin-based quantum information
science, RKKY interaction in low dimensions,
Topological quantum matters, Majorana fermions and
parafermions
Single-spin manipulation in a double
quantum dot in the field of a micro-magnet
We examine an electron spin manipulation scheme based on inhomogeneous magnetic
fields, which is directly applicable to realistic GaAs double dot setups with a built-in
micro-magnet design. The manipulation of single spins in quantum dots by the exchange
interaction and inhomogeneous magnetic field was previously discussed in literature.
However, a large inhomogeneity is difficult to achieve through the slanting field of a
micro-magnet in current lateral double dots. We therefore developed an alternative
scheme, which makes manipulation times of nanosecond for realistic parameters
possible. Our results show how to realize quantum bits allowing for fast operations with
high fidelities compatible with existing semiconductor quantum dot technology.
Brief resume
1992 Doctor of Science, Department of Physics, Faculty of
Science, University of Tokyo
Brief resume
1985 Ph.D. in Theoretical Physics, University of Zurich,
Switzerland
1985 Postdoctoral Research Associate, University of Zurich,
Switzerland
1989 Postdoctoral Research Fellow, University of Illinois at
Urbana-Champaign, USA
1991 Research Scientist, IBM T. J. Watson Research Center,
USA
1993/5 Assistant/Associate Professor, Simon Fraser University,
Canada
1996 Professor, Department of Physics, University of Basel,
Switzerland (-present)
2012 Team Leader, Emergent Quantum System Research
Team, RIKEN
2013 Team Leader, Quantum System Theory Research Team,
Outline
Emergent spin electromagnetism induced
by magnetization textures in the presence of
spin-orbit interaction
Magnetic textures in metallic systems induces emergent electromagnetic fields which
couples to electrons' spin. We have studied the emergent fields induced by spin-orbit
interactions and showed that Rashba spin-orbit interaction induces spin electromagnetic
field which arises in the linear order in gradient of magnetization texture, in contrast to the
conventional spin Berry’s phase contributions. The Rashba-induced effective electric and
1992 Postdoctoral Fellow, The Department of Physics, Faculty
of Science, University of Tokyo
1994 Postdoctoral Fellow, The Institute of Physical and
Chemical Research, RIKEN
1996 Assistant Professor, Graduate School of Science, Osaka
University
2004 PRESTO, Japan Science and Technology Agency
2005 Associate Professor, Graduate School of Science and
Engineering, Tokyo Metropolitan University
2012 Team Leader, Emergent Spintronics Theory Research
Team, RIKEN
2013 Team Leader, Spin Physics Theory Research Team,
magnetic fields satisfy in the absence of spin relaxation the Maxwell’s equations as in the
charge-based electromagnetism. When spin relaxation is taken into account besides spin
Outline
dynamics, a monopole current emerges. It induces a novel monopole-driven spin motive
force whose origin is different from the conventional motive force induced by the
time-dependent spin Berry’s phase. The monopole is expected to play an important role in
spin-charge conversion and in the integration of spintronics into electronics.
Upper panel: Geometries used in the simulations showing the position of the two quantum
dots (red dots 1,2) and the micro-magnet (green metal plate). Lower panel: Detuning pulses
to initialize the system from the initial position (I) into the logical subspace at A (blue), to do
single-spin rotations at B (red), and to read out the logical states (green). Copyright APS.
Publications
1. S. Chesi, X. J. Wang, J. Yoneda, T. Otsuka, S. Tarucha, and D. Loss, “Single-spin manipulation in a double
quantum dot with micromagnet”, Phys. Rev. B, 90, 235311 (2014).
2. P. Stano, and D. Loss, “NMR Response of Nuclear Spin Helix in Quantum Wires with Hyperfine and
Spin-Orbit Interaction”, Phys. Rev. B, 90, 195312 (2014).
3. T. Meng, P. Stano, J. Klinovaja, and D. Loss, “Helical nuclear spin order in a strip of stripes in the Quantum
Hall regime”, Eur. Phys. J. B, 87, 203 (2014).
4. P. Scarlino, E. Kawakami, P. Stano, M. Shafiei, C. Reichl, W. Wegscheider, and L. M. K. Vandersypen, “Spin
relaxation anisotropy in a GaAs quantum dot”, Phys. Rev. Lett., 113, 256802 (2014).
5. F. Nichele, S. Chesi, S. Hennel, A. Wittmann, Ch. Gerl, W. Wegscheider, D. Loss, T. Ihn, and K. Ensslin,
“Characterization of spin-orbit interactions of GaAs heavy holes using a quantum point contact”, Phys.
Rev. Lett., 113, 046801 (2014).
30
Our team is working on the quantum theory of
condensed matter with a focus on spin and phase
c o h e re n t p h e n o m e n a i n s e m i c o n d u c t i n g a n d
magnetic nanostructures. In particular, the team
investigates the fundamental principles of quantum
information processing in the solid state with a focus
on spin qubits in quantum dots, superconducting
qubits, and topological quantum states such as
Majorana fermions and parafermions. This involves
the study of decoherence in many-body systems and
scalable quantum computing technologies based on
surface codes and long-distance entanglement
schemes. We also study nuclear spin phases,
many-body effects in low-dimensional systems,
quantum Hall effect, topological matter, spin orbit
interaction, and quantum transport of magnetization.
Core members
(Senior Research Scientist) Peter Stano
Jin-Hong Park, Chen-Hsuan Hsu, Guang Yang
(Student Trainee) Ongjen Malkoc
In ferromagnetic metals, spin of electrons traveling through a magnetization structure
follows the local spin and acquires a quantum phase. This phase acts as an effective
electromagnetic fields that couples to electron spin.
Publications
1. K.-J. Kim, R. Hiramatsu, T. Koyama, K. Ueda, Y. Yoshimura, D. Chiba, K. Kobayashi, Y. Nakatani, S.
Fukami, M. Yamanouchi, H. Ohno, H. Kohno, G. Tatara, and T. Ono, “Two-barrier stability that allows
low-power operation in current-induced domain-wall motion”, Nat. Commun., 4, 2011 (2013).
2. G. Tatara, N. Nakabayashi, and Kyun-Jin Lee, “Spin motive force induced by Rashba interaction in the
strong sd coupling regime”, Phys. Rev. B, 87, 054403 (2013).
Our aim is to explore novel spin-related effects with
extremely high efficiency in condensed matters. We
thus contributes to development of spintronics, a
technology using spin as well as charge of electrons,
and to realization of ultrafast and high-density
information technology with low energy consumption.
Our particular interest is at present in a strong
quantum relativistic effect in solids, which is applicable
to very strong magnets and efficient conversion of spin
information to an electric signal. Our main method is a
field theory.
Core members
(Research Scientist) Henri Mikael Saarikoski
Toru Kikuchi, Nguyen Thanh Phuc,
Naoya Arakawa, Yan-Ting Chen
(Junior Research Associate) Hideo Kawaguchi
3. F. Nagasawa, D. Frustaglia, H. Saarikoski, K. Richter and J. Nitta, “Control of the spin geometric phase
in a semiconductor quantum ring”, Nat. Commun., 4, 2526 (2013).
4. T. Yokoyama, M. Eto, and Y. V. Nazarov, “Josephson Current through Semiconductor Nanowire with
Spin-Orbit Interaction in Magnetic Field”, J. Phys. Soc. Jpn., 82, 054703 (2013) .
5. K. Taguchi, J. Ohe, and G. Tatara, “Ultrafast magnetic vortex core switching driven by topological
inverse Faraday effect”, Phys. Rev. Lett., 109, 127204 (2012).
31
Emergent Matter Science Research
Support Team
Quantum Effect Device Research Team
Hikota Akimoto (Ph.D.), Team Leader
Koji Ishibashi (D.Eng.), Team Leader
hikota@riken.jp
kishiba@riken.jp
Research field
Research field
Engineering, Physics
Keywords
Keywords
Nanometer scale fabrication, Sample characterization,
Education of users
Carbon nanotube, Semiconductor nanowire,
Quantum dots, Nanodevices
Brief resume
Brief resume
1988 D.Eng., Graduate School of Electrical Engineering,
Osaka University
1990 Ph.D., Osaka City University
Supporting researchers for
nanometer-scale fabrication
1996 Visiting Scientist, Leiden University, Netherlands
1998 Post Doctoral Associate, University of Florida, USA
2001 Senior Post Doctoral Associate, University of
Massachusetts, USA
To build a sustainable society with environment friendly device, it is essential to realize
energy effective devices and faster information process. To realize such devices, the
researchers in the Center for Emergent Matter Science are enthusiastically pursuing to
develop quantum devices, spin devices and quantum computers. In building such devices,
highly sophisticated equipment and support for keeping best condition of the equipment
2003 Development Researcher, Nanoscience Development
and Support Team, RIKEN
2008 Team Head, Nanoscience Development and Support
Team, RIKEN
2013 Team Leader, Emergent Matter Science Research
Support Team, Quantum Information Electronics
(-present)
are required.
Carbon nanotube/molecule heterojunctions
to form molecular scale nanostructures
Ends of the single-wall carbon nanotubes (SWCNT) can be chemically modified to
introduce chemical groups, such as a carboxyl group and an amino group. With these,
molecules can be chemically combined to form the SWCNT/molecule heterojunctions,
which makes it possible to realize one-dimensional band-gap engineering with molecules
as a tunnel barrier, as have been widely done with semiconductor superlattices and
quantum wells. The figure shows examples of the fabricated structures with the
Our team is established to support the researcher’s activity by providing skillful expertise.
Outline
1991 Researcher, Semiconductor Laboratory, RIKEN
1996 Visiting Researcher, Delft University of Technology, The
Netherlands
2003 Chief Scientist, Advanced Device Laboratory, RIKEN
(-present)
2003 Adjunct Professor, Chiba University (-current)
2005 Adjunct Professor, Tokyo University of Science (-present)
2008 Adjunct Professor, Tokyo Institute of Technology
(-present)
2013 Team Leader, Quantum Effect Device Research Team,
SWCNT/molecule heterojunctions. In Fig. (a), three different SWCNTs are connected with
the molecules, which would be an analogue of the one-dimensional single quantum-well
We are responsible for operation of the equipment like lithography systems including an
1988 Researcher, Frontier Research Program, RIKEN
Outline
structures. The SWCNT in the center could be used as a single quantum dot when the
electron beam lithography, an maskless UV photo lithography system, deposition systems
other two were used as a lead for the transport measurements. The advantage of using
like evaporators and sputters, dry and wet etching systems and observation system as
the collagen model peptide is that the length of the molecule can be controlled digitally
scanning electron microscopy and for keeping them in the best condition. We instruct
(Fig.1(b)). An isolated single quantum dot was fabricated in a SWCNT with both ends
users in the usage of equipment and provide technical information in fabrication. WIth our
terminated by the molecules. A very unique feature of using the molecular heterojunction
effort, the researchers are now able to fabricate and characterize various devices in the
is that the shape of the confinement potential can be modified by a electric dipole
range of 10 nm – 10 µm tirelessly.
moment of the molecule, the direction of which is controlled by the type of chemical
bonding between the SWCNT and the molecule. These features are confirmed by the
Examples of the
specimen fabricated
in the clean room.
Publications
1. H. Ikegami, H. Akimoto, D. G. Rees, and K. Kono, “Evidence for Reentrant Melting in a
Quasi-One-Dimensional Wigner Crystal”, Phys. Rev. Lett., 109, 236802 (2012).
2. M. Shimizu, H. Akimoto, K. Ishibashi, “Electronic Transport of Single-Wall Carbon Nanotubes with
Superconducting Contacts”, Jpn. J. Appl. Phys., 50, 035102 (2011).
3. S. M. Huang, Y. Tokura, H. Akimoto, K. Kono, J. J. Lin, S. Tarucha, K. Ono., “Spin Bottleneck in Resonant
Tunneling through Double Quantum Dots with Different Zeeman Splittings”, Phys. Rev. Lett., 104, 136801
(2010).
32
Our mission is to develop novel technologies with a
wide range of applications in nanoscience and
nanotechnology and to support the users in Riken for
nanometer-scale fabrication and the characterization
of specimens. We are responsible for the operation of
the facilities including the clean room and the chemical
rooms with suitable safety measure. The clean room is
for fabrication and characterization of nanometer-scale
devices and the chemical rooms are for those of wet
samples for chemistry and biology. In the clean room
and the chemical rooms, more than 30 apparatus
have been installed and are open to the users. We are
also responsible for the education of the users
Core members
(Technical Staff) Ryoji Itoh, Kazuhiko Shihoyama
scanning tunneling spectroscopy method.
(a) Scanning tunneling image of three
different single-wall carbon nanotubes
chemically connected with molecules.
(b) Zoom-up image of the connection part.
(c) Individual single-wall carbon nanotube
with both ends terminated by molecules for
optical study.
Taken from K. Ishibashi, R. S. Deacon and
A. Hida, to be published in OYOBUTURI,
84 (2015) (in Japanese) Copy Right: JSAP
Publications
1. A. Hida, and K. Ishibashi, “Molecule-induced quantum confinement in single-walled carbon nanotube”,
Appl. Phys. Express, 8, 045101 (2015).
2. X. Zhou, J. Hedberg, Y. Miyahara, P. Grutter, and K. Ishibashi, “Scanning gate imaging of two coupled
quantum dots in single-walled carbon nanotubes”, Nanotechnology, 25 495703 (2014).
3. X. Zhou, and K. Ishibashi, “Single charge detection in capacitively coupled integrated single electron
transistors based on single-walled carbon nanotubes”, Appl. Phys. Lett., 101, 123506 (2012).
4. H. Nakamura, H. Tomita, H. Akimoto, R. Matsumura, I. Inoue, T. Hasegawa, K. Kono, Y. Tokura, H. Takagi,
“Tuning of Metal-Insulator Transition of Quasi-Two-Dimensional Electrons at Parylene/SrTiO3 Interface by
Electric Field”, J. Phys. Soc. Jpn., 78, 083713 (2009).
4. T. Nishio, T. Kozakai, S. Amaha, M. Larsson, H. Nilsson, H. Q. Xu, G. Q. Zhang, K. Tateno, H. Takayanagi,
and K. Ishibashi, “Supercurrent through InAs nanowires with highly transparent superconducting
contacts”, Nanotechnology, 22, 445701 (2011).
5. H. Akimoto, J. S. Xia, D. Candela, W. J. Mullin, E. D. Adams, N. S. Sullivan, “Giant viscosity enhancement
in a spin-polarized fermi liquid”, Phys. Rev. Lett., 99, 095301 (2007).
5. S. Moriyama, D. Tsuya, E. Watanabe, S. Uji, M. Shimizu, T. Mori, T. Yamaguchi, and K. Ishibashi,
“Coupled quantum dots in a graphene-based two-dimensional semimetal”, Nano Lett., 9, 2891 (2009).
We study quantum effects that appear in nanoscale
structures and apply them to functional nanodeives.
Nanomaterials that are formed in a self-assemble
manner, such as carbon nanotubes, graphene and
semiconductor nanowires (Si/Ge, InAs, InSb) are used
as building blocks for extremely small nanostructures,
and are combined with top-down nanofabrication to
fabricate functional nanodevices with a sub-10nm
scale. We focus on hybrid nanostructures, such as
carbon nanotube/molecule heterostructures and
nanostructures/superconductor hybrid nanostructures,
to realize unique functionalities that enable us to
control electrons, photons, excitons, cooper pairs and
plasmons on a single quantum level. With those, we
develop single electron devices and circuits, quantum
information devices and plasmonic and photovoltaic
devices for future low-power nanoelectronics.
Core members
(Senior Research Scientist) Takayuki Okamoto,
Takafumi Sassa, Keiji Ono, Jobu Matsuno
(Research Scientist) Russell D. Deacon
(Technical Staff) Masaru Mihara
33
Quantum Condensed Phases Research Team
Superconducting Quantum Simulation
Research Team
Kimitoshi Kono (D.Sci.), Team Leader
Jaw-Shen Tsai (Ph.D.), Team Leader
kkono@riken.jp
tsai@riken.jp
Research field
Research field
Low Temperature Physics
Keywords
Keywords
Superfluidity, Surface Phenomena, Two-dimensional
electron system, Microwave, Nanodevices, Quantum
computing
Superconductivity, Josephson effect, Quantum
coherence, Qubit, Artificial atoms
Brief resume
Brief resume
1983 Ph.D., State University of New York at Stony Brook, USA
1982 D.Sci., University of Tokyo
1982 Research Associate, Hyogo University of Teacher
Education
Novel phenomena
in surface charges on liquid helium
1987 Associate Professor, Hyogo University of Teacher
Education
Free surface of liquid helium provides a super-clean substrate to support
two-dimensional electrons and ions. Moreover, free surface of superfluid He may
3
support Majorana surface bound states, which is closely related with a topological
superfluid, and hence, it is an ideal play ground to study the most typical emergent
phenomena.
Our team achieved a single electron transport of electrons on a capillary condensed He
channel, for the first time. In a quasi-one dimensional channel we succeeded in
observing the corrugation of phase boundary between the Wigner (electron) solid and
Quantum Optics with
Superconducting Artificial Atoms (Qubit)
1989 Associate Professor, Institute of Physics, University of
Tsukuba
We realize deterministic control of quantum state of a superconducting artificial atom by
1992 Associate Professor, Institute for Solid State Physics,
University of Tokyo
single microwave photon. It was achieved by an impedance-matched Λ-type three-level
2000 Chief Scientist, Low Temperature Physics Laboratory,
RIKEN
2013 Team Leader, Quantum Condensed Phases Research
Team, Quantum Information Electronics Division, RIKEN
Outline
electron liquid as shown in Fig. 1. This is due to the enhancement and suppression of
system using dressed states in a circuit QED setup, where a superconducting flux qubit
and a coplanar waveguide resonator are coupled capacitively. We experimentally observe
that the incident microwave is perfectly absorbed and is down-converted with an
efficiency of ~70%
With the above circuit, by reading out the final quantum state of the artificial atom,
atom, we demonstrate two-mode correlated emission lasing. Correlation of two different
along the channel and unstable configurations between them.
color emissions reveals itself as equally narrowed linewiths and quench of their mutual
In the transport measurement of ions under the free surface of superfluid 3He-A, we
phase-diffusion. The mutual linewidth is more than four orders of magnitude narrower
than the Schawlow-Townes limit.
first observed the Hall effect like transversal current due to skew scattering of
quasiparticles from ions. The skew is a direct evidence of the chirality of superfluid 3He-A,
Utilizing a flux qubit coupled to two half open space consist of coplanar wave guides,
which results from an anisotropy vector associated with angular momentum of superfluid
we realized an on-demand single microwave photon source with adjustable frequency
order parameter.
and efficiency of ~70%.
Solid-liquid phase diagram of
quasi-one dimensional electrons on
H e c h a n n e l . A b l a c k re g i o n i s
i n s u l a t i n g w h e re e l e c t ro n s a re
depleted from the channel. By
e n t e r i n g a c o l o re d c o n d u c t i n g
region, electron rows form one by
one. The consecutive formation of
electron row produces corrugation
of phase boundary. Inset shows the
device used in the measurement.
We will develop techniques to manipulate single
electrons and ions trapped at an extremely clean
surface of liquid helium, which will be utilized to
fabricate quantum effect devices. This includes lateral
confinement techniques and control of quantum
transitions between discrete energy levels due to the
abovementioned confinement and due to surface
states, and laser spectroscopy of ions (atoms). In
a d d i t i o n , s u p e r fl u i d i t y , a t y p i c a l e m e r g e n t
phenomenon, will be studied in the context of
topological properties associated with a spontaneous
symmetry breaking.
Core members
Publications
1. H. Ikegami, Y. Tsutsumi, and K. Kono, “Chiral Symmetry Breaking in Superfluid 3He-A”, Science, 341, 59
(2013).
2. H. Ikegami, H. Akimoto, D. G. Rees, and K. Kono, “Evidence for Reentrant Melting in a
Quasi-One-Dimensional Wigner Crystal”, Phys. Rev. Lett., 109, 236802 (2012).
3. D. G. Rees, I. Kuroda, C. A. Marrache-Kikuchi, M. Höfer, P. Leiderer, and K. Kono, “Point-Contact
Transport Properties of Strongly Correlated Electrons on Helium”, Phys. Rev. Lett., 106, 026803 (2011).
(Research Scientist) Petr Moroshkin
Kostyantyn Anatoliyovych Nasyedkin, Yu-Chen Sun
(Special Postdoctoral Researcher) Daisuke Sato
(Junior Research Associate) Tomoya Tsuiki
(Temporary Employee) Yuichi Okuda
2000 Fellow, American Physical Society, USA
2001 Fellow, Nano Electronics Research Laboratories, NEC
2001 Team Leader, Macroscopic Quantum Coherence Team,
RIKEN
2012 Group Director, Single Quantum Dynamics Research
Group, RIKEN
2013 Team Leader, Macroscopic Quantum Coherence
2014 Team Leader, Superconducting Quantum Simulation
(-present)
2015 Professor, Tokyo University of Science (-present)
single microwave photon detection is achieved with near 75% efficiency.
Bringing a pair of harmonic oscillators into resonance with transitions of the three-level
solidification associated with a consecutive formation of stable structure of electron rows
1983 Research Scientist, Microelectronics Research
Laboratories, NEC
Experimentally observe frequency
down-convertion with an efficiency
of ~70%.
K. Inomata et al, Phys. Rev. Lett.
113, 063604 (2014)
Outline
We are studying macroscopic quantum coherence
that occurs in small Josephson junction circuits. In the
system, charge and phase degrees of freedoms
co-exist, and their coherent control can be exploited
as quantum bit (qubit), the basic component of the
quantum computer. Superconducting qubit possesses
high degree of freedoms in the circuit design and
ability to local control as well as readout quantum
states. Utilizing these properties, the development of
small scale quantum analog simulator that aiming for
the simulations of macroscopic material properties is
targeted. Study of non-equilibrium quantum dynamics
in these circuits is also planned.
Core members
(Research Scientist) Peng Zhihui, Simon Devitt
Publications
1. O. V. Astafiev, L. B. Ioffe, S. Kafanov, Yu. A. Pashkin, K. Yu. Arutyunov, D. Shahar, O. Cohen, and J. S.
Tsai, “Coherent quantum phase slip”, Nature, 484, 355 (2012).
2. A. O. Niskanen, K. Harrabi, F. Yoshihara, Y. Nakamura, and J. S. Tsai, “Quantum Coherent Tunable
Coupling of Superconducting Qubits”, Science, 316, 723 (2007).
3. T. Yamamoto, Yu. Y. Pashkin, O. V. Astafiev, Y. Nakamura, and J. S. Tsai, “Demonstration of conditional
gate operation using superconducting charge qubits”, Nature, 425, 941 (2003).
4. Yu. A. Pashkin, T. Yamamoto, O. V. Astafiev, Y. Nakamura, D. V. Averin, and J. S. Tsai, “Quantum
oscillations in two coupled charge qubits”, Nature, 421, 823 (2003).
5. Y. Nakamura, Yu. A. Pashkin, and J. S. Tsai, “Coherent Control of Macroscopic Quantum States in a
Single-Cooper-pair Box”, Nature, 398, 786 (1999).
34
35
Cross-Divisional Materials Research Program
Emergent Spintronics Research Unit
Dynamic Emergent Phenomena Research Unit
Shinichiro Seki (D.Eng.), Unit Leader
Fumitaka Kagawa (D. Eng.), Unit Leader
shinichiro.seki@riken.jp
fumitaka.kagawa@riken.jp
Research field
Research field
Physics, Engineering, Chemistry, Materials Sciences
Keywords
Keywords
Spintronics, Multiferroics, Strongly correlated electron
system
Strongly correlated electron system, Organic
ferroelectrics, Scanning probe microscopy,
Spectroscopy
Brief resume
Brief resume
2010 Ph.D. in Applied Physics, University of Tokyo
Observation of
skyrmions in a multiferroic material
Magnetic skyrmion is a topologically stable particle-like object, which appears as
nanometer-scale vortex-like spin texture in a chiral-lattice magnet. In metallic materials,
2010 Research Associate, Quantum-Phase Elecrtonics
Center, University of Tokyo
2012 Lecturer, Quantum-Phase Elecrtonics Center, University
of Tokyo
2012 PRESTO Researcher, Japan Science and Technology
Agency (-present)
2013 Unit Leader, Emergent Spintronics Research Unit,
Cross-Divisional Materials Research Program, RIKEN
electrons moving through skyrmion spin texture gain a nontrivial quantum Berry phase,
which provides topological force to the underlying spin texture and enables the
2006 Research fellowship for young scientists
Demonstration of correlated-electron
phase-change memory
2007 Researcher, JST-ERATO Multiferroic project
2010 Project Lecturer, Quantum-Phase Electronics Center,
University of Tokyo
An aggregation of interacting atoms condenses into either a crystal or non-equilibrium
glass depending on cooling speed. Chalcogenide phase-change memory (PCM), a
promising candidate for next-generation non-volatile memories, exploits such an
Outline
2012 Lecturer, Department of Applied Physics, University of
Tokyo
2013 Unit Leader, Dynamic Emergent Phenomena Research
Unit, Cross-Divisional Materials Research Program,
atom-configuration degree of freedom as optically or electrically switchable state
current-induced manipulation of magnetic skyrmion. Such electric controllability, in
variables. The unique memory concept has thus far been used exclusively in an
addition to the particle-like nature, is a promising advantage for potential spintronic device
aggregation of atoms. Here, we demonstrate a new class of PCM emerging from a
applications. Recently, we newly discovered that skyrmions appear also in an insulating
charge-configuration degree of freedom in strongly correlated electrons. Repeatable
chiral-lattice magnet Cu2 OSeO3 . We find that the skyrmions in insulator can magnetically
switching between a high-resistivity charge-crystalline (or charge-ordered) state and a
induce electric polarization through the relativistic spin-orbit interaction, which implies
low-resistivity quenched state, charge glass, is achieved via both optical and electrical
possible manipulation of the skyrmion by external electric field without loss of joule
heating in organic conductors. A faster correlated-electron PCM is developed by
heating. The present finding of multiferroic skyrmion may pave a new route toward the
exploiting a material that requires faster quenching to kinetically avoid charge
engineering of novel magnetoelectric devices with high energy efficiency.
crystallization. Our results establish a clear case whereby practically stable glassy
Outline
electronic states hidden behind long-range ordered states can be uncovered by adopting
Core members
Publications
1. M. Mochizuki and S. Seki, “Magnetoelectric resonances and predicted microwave diode effect of the
skyrmion crystal in a multiferroic chiral-lattice magnet”, Phys. Rev. B, 87, 134403 (2013).
36
(Postdoctoral Researcher) Rina Takagi
hitherto-untried quenching rates and thus underlies a novel PCM.
Charge glass
SET
RESET
(High resistivity)
(Low resistivity)
t
Resistance (Ω)
t
+0.85
+0.15
RESET
108
Voltage (V)
Laser or
current
SET
Charge crystal
Laser or
current
Crystal structure of chiral-lattice insulator Cu2OSeO3,
and magnetic skyrmion inducing electric polarization.
The electronics utilizing spin degree of freedom is
called spintronics, and considered as a key to realize
novel device with unique function and low energy
consumption. By bringing the knowledge of solid state
chemistry and material science to the spintronics field
where only simplest ferromagnetic materials have
been investigated, we newly create appropriate
environment for electrons to show up various
emergent spin functionality. We try to build up the new
fundamental science and technology for extremely
energy efficient magnetic storage/computing device,
especially by combining the state-of-art concepts
such as (1) nanometric spin vortex with particle nature
(magnetic skyrmion), (2) electric control of magnetism,
and (3) spin current as dissipationless information
carrier.
107
Charge
crystal
106
105
104
103
Charge
liquid
Charge
crystal
Charge
glass
40
20
0
0
50
100
Time (s)
150
Concept of correlated-electron phase-change memory (left) and its demonstration (right)
Publications
1. H. Oike, F. Kagawa, N. Ogawa, A. Ueda, H. Mori, M. Kawasaki, and Y. Tokura, “Phase-change memory
function of correlated electrons in organic conductors”, Phys. Rev. B, 91, 041101(R) (2015).
2. S. Seki, X. Z. Yu, S. Ishiwata, and Y. Tokura, “Observation of Skyrmions in a Multiferroic Material”, Science,
336, 198 (2012).
2. F. Kagawa, S. Horiuchi, N. Minami, S. Ishibashi, K. Kobayashi, R. Kumai, Y. Murakami, and Y. Tokura,
“Polarization Switching Ability Dependent on Multidomain Topology in a Uniaxial Organic Ferroelectric”,
Nano Lett., 14, 239 (2014).
3. S. Seki, N. Kida, S. Kumakura, R. Shimano, and Y. Tokura, “Electromagnons in the spin collinear state of
a triangular lattice antiferromagnet”, Phys. Rev. Lett., 105, 097207 (2010).
3. F. Kagawa, T. Sato, K. Miyagawa, K. Kanoda, Y. Tokura, K. Kobayashi, R. Kumai, and Y. Murakami,
“Charge-cluster glass in an organic conductor”, Nat. Phys., 9, 419 (2013).
4. S. Seki, H. Murakawa, Y.Onose, and Y. Tokura, “Magnetic digital flop of ferroelectric domain with fixed spin
chirality in a triangular lattice helimagnet”, Phys. Rev. Lett., 103, 237601 (2009).
4. F. Kagawa, S. Horiuchi, M. Tokunaga, J. Fujioka, and Y. Tokura, “Ferroelectricity in one-dimensional
organic quantum magnet”, Nat. Phys., 6, 169 (2010).
5. S. Seki, Y.Onose, and Y. Tokura, “Spin-driven ferroelectricity in triangular lattice antiferromagnets ACrO2 (A
= Cu, Ag, Li, or Na) ”, Phys. Rev. Lett., 101, 067204 (2008).
5. F. Kagawa, K. Miyagawa, and K. Kanoda, “Unconventional critical behaviour in a quasi-two-dimensional
organic conductor”, Nature, 436, 534 (2005).
Our unit explores dynamic phenomena exhibited by
strongly correlated electron systems in both bulk and
device structures to construct a new scheme for
scientific investigation. In particular, we study
external-field-driven dynamic phenomena exhibited by
sub-micron-scale structures, such as topological spin
textures and domain walls, using spectroscopy of
dielectric responses and resistance fluctuations from
the millihertz to gigahertz region. We also pursue
real-space observations and measurements of local
physical properties using scanning probe microscopy
as a complementary approach. We are aiming to
control novel physical properties exhibited by
topological structures in condensed matter systems
on the basis of knowledge obtained from these
methods.
Core members
(Postdoctoral Researcher) Hiroshi Oike
37
Physicochemical Soft Matter Research Unit
Quantum Many-Body Dynamics Research Unit
Fumito Araoka (Dr. Eng.), Unit Leader
Takeshi Fukuhara (D. Sci.), Unit Leader
fumito.araoka@riken.jp
takeshi.fukuhara@riken.jp
Research field
Research field
Physical and Structural Properties of
Functional Organic Materials
Keywords
Keywords
Quantum simulation, Quantum computing, Cold
atoms, Bose-Einstein condensation, Optical lattice
Liquid crystals, Polymeric materials, Soft-matter
physics, Optical properties, Organic nonlinear optics,
Organic ferroelectrics
Brief resume
2009 D. Sci., Kyoto University
Brief resume
Discovery of the first genuine ferroelectric
columnar liquid crystal
2003 Ph.D in Engineering, Tokyo Institute of Technology,
Japan
- Towards paintable high-performance organic ferroelectric devices -
2005 Postdoctoral Researcher, The University of Tokyo
Recently, we have discovered a brand-new type of ferroelectricity in a hexagonal
columnar mesophase in a wedge-shaped molecular system, that is, an axially ferroelectric
columnar liquid crystal (FCLC). The FCLC phase accommodates the cylindrical columns
of 1D stacks of umbrella-like assemblies consisting of three or four wedge-shaped
molecules. Therefore in this system, reversible and sustainable spontaneous polarization
2003 Postdoctoral Researcher, Catholic University of Leuven,
Belgium
2006 Postdoctoral Researcher, Tokyo Institute of Technology
Ultracold atoms in an optical lattice can emulate several fundamental models in
2007 Assistant Professor, Tokyo Institute of Technology
condensed matter physics. An important example is a quantum spin system described by
2013 Unit Leader, Physicochemical Soft-Matter Research Unit,
the Heisenberg Hamiltonian. In the ultracold-atom experiment, there exists less
applications, such as high-density memories in which each single column acts as one bit,
and tracked their dynamics with high resolution in space and time. In the single impurity
or nano-piezo elements. Another advantage for the use of FCLC is a brilliant
case, coherent propagation of the impurity, or a quantum walk of the magnon, was
wet-processability. For instance, high optical-quality thin ferroelectric films can be formed
observed. Different from the single-spin dynamics, spin-spin interaction becomes
even on curved surfaces, simply by casting the FCLC
important when flipping two spins, and results in the formation of bound states. These
solution followed by a remote electric field application.
two-magnon bound states were predicted to exist in Heisenberg chains by H. Bethe
Besides, we have succeeded in visualization of
more than 80 years ago. Investigating the spatial correlations after dynamical evolution,
f e r ro e l e c t r i c s w i t c h i n g i n F C L C b y m e a n s o f
we identified the bound states, and observed their dynamics. This novel microscopic
of spontaneous polarization and its reversal.
These achievements are a result of the successful
collaboration with Aida group.
(A) Ferroelectric columnar liquid crystal (FCLC), (B) Conceptual
drawing of an ultra-high density memory, (C) Appearance of a
high-optical quality FCLC film, (D, E) Ferroelectricity as visualized
by (D) KFM and (E) ISHM.
Publications
Publications
1. F. Araoka, S. Masuko, A. Kogure, D. Miyajima, T. Aida, and H. Takezoe, “High-Optical-Quality Ferroelectric
Film Wet-Processed from a Ferroelectric Columnar Liquid Crystal as Observed by Non-linear-Optical
Microscopy”, Adv. Mater., 25, 4014 (2013).
2. F. Araoka, G. Sugiyama, K. Ishikawa, and H. Takezoe, “Highly-ordered Helical Nanofilament Assembly
Aligned by Nematic Director Field”, Adv. Func. Mater., 23, 2701 (2013).
3. T. Ueda, S. Masuko, F. Araoka, K. Ishikawa, and H. Takezoe, “A General Method for the Enantioselective
Formation of Helical Nanofilaments”, Angew. Chem. Int. Ed., 27, 6863 (2013).
4. G. Lee, R. J. Carlton, F. Araoka, N. L. Abbott, and H. Takezoe, “Amplification of the stereochemistry of
biomolecular adsorbates by deracemization of chiral domains in bent-core liquid crystals”, Adv. Mater., 25,
245 (2013).
5. D. Miyajima, F. Araoka, H. Takezoe, J. Kim, T. Kato, M. Takata, and T. Aida, “Ferroelectric Columnar Liquid
Crystal Featuring Confined Polar Groups Within Core-Shell Architecture”, Science, 336, 209 (2012).
Outline
Starting from a fully magnetized one-dimensional spin chain, we deterministically
created mobile spin impurities (locally excited magnons) by selectivelly flipping the spins,
the latter enables the detection of the directional sense
2014 Unit Leader, Quantum Many-Body Dynamics Research
dissipation and less decoherence, which enable us to investigate out-of-equilibrium
directs along the columnar axis. Such a new material may open up a possibility of novel
second-harmonic (ISHM) microscopies. Particularly,
2010 Postdoctoral researcher, Max Planck Institute of
Quantum Optics, Germany
quantum dynamics in such spin systems.
Outline
method can be used for studying more complex magnetic many-body states, and also
K e l v i n - P ro b e f o rc e ( K F M ) a n d i n t e r f e ro m e t r i c
38
Dynamics of quantum spin systems
using ultracold atoms in an optical lattice
2009 Researcher, ERATO Ueda Macroscopic Quantum
Control Project, Japan Science and Technology Agency
“Physicochemical Soft Matter Research Unit” is mainly
working on functionality of soft-matter systems from
the viewpoints of physical experiments and analyses.
In our research unit, particular attention is paid to
liquid crystals due to their self-organizability leading to
multifarious structures in which many interesting
physical phenomena emerge. Our interest also covers
potential applications of such soft-matter systems
towards optical/electronic or chemical devices. For
example, 1. Ferroelectric interactions and switching
mechanisms in novel liquid crystalline ferroelectric
materials, 2. Chirality related phenomena - origin and
control of emergence, as well as applications of
superstructure chirality in self-organized soft-matter
systems, 3. Novel optical/electronic devices based on
self-organized soft-matter systems.
Core members
Venkata Subba Rao Jampani, Satoshi Aya
dynamical evolution of quantum correlations.
Spatial correlations after
dynamical evolution.
Experimental result (left) and
numerical simulation (right).
Publications
Publications
Modern technology has been progressed based on
understanding of quantum many-body systems. In
addition to the conventional study of equilibrium
states, non-equilibrium dynamics plays an important
role in developing further intriguing materials and
advancing quantum information processing
technology. In this research unit, we investigate
non-equilibrium dynamics of quantum many-body
systems using ultracold atomic gases. Advantages of
ultracold-atom experiments are simplicity and
excellent controllability of the parameters, including
dimensions, of the systems. Especially, a quantum
gas loaded into periodic potential generated by a laser
(optical lattice) can mimic fundamental models in the
strongly correlated physics, and it can be used as a
platform for quantum information processing. Utilizing
such systems, we investigate real-time and real-space
dynamics, and also control the many-body dynamics.
1. P. Schauß, J. Zeiher, T. Fukuhara, S. Hild, M. Cheneau, T. Macrì, T. Pohl, I. Bloch, and C. Gross,
“Crystallization in Ising quantum magnets”, Science, 347, 1455 (2015).
2. S. Hild, T. Fukuhara, P. Schauß, J. Zeiher, M. Knap, E. Demler, I. Bloch, and C. Gross,
“Far-from-Equilibrium Spin Transport in Heisenberg Quantum Magnets”, Phys. Rev. Lett., 113, 147205
(2014).
3. T. Fukuhara, P. Schauß, M. Endres, S. Hild, M. Cheneau, I. Bloch, and C. Gross, “Microscopic
observation of magnon bound states and their dynamics”, Nature, 502, 76 (2013).
4. T. Fukuhara, A. Kantian, M. Endres, M. Cheneau, P. Schauß, S. Hild, D. Bellem, U. Schollwöck, T.
Giamarchi, C. Gross, I. Bloch, and S. Kuhr, “Quantum dynamics of a mobile spin impurity”, Nat. Phys.,
9, 235 (2013).
5. M. Endres, T. Fukuhara, D. Pekker, M. Cheneau, P. Schauß, C. Gross, E. Demler, S. Kuhr, and I. Bloch,
“The ‘Higgs’ Amplitude Mode at the Two-Dimensional Superfluid/Mott Insulator Transition”, Nature,
487, 454 (2012).
39
Emergent Photodynamics Research Unit
Quantum Surface and Interface Research Unit
Naoki Ogawa (D. Eng.), Unit Leader
Shuaihua Ji (Ph.D.), Unit Leader
naoki.ogawa@riken.jp
shuaihua.ji@riken.jp
Research field
Research field
Physics, Material Science
Physics, Materials Sciences, Engineering
Keywords
Keywords
Strongly correlated electron system, Spin-orbit
interaction, Ultrafast spectroscopy, Spintronics
Scanning tunneling microscopy, Low dimensional
superconductors, Topological quantum matters, Thin
films and interfaces, Surface and heterogeneous
interfaces
Brief resume
2004 D. Eng., University of Tokyo
Brief resume
2004 Postdoctoral Associate, University of California at Irvine
Photoinduced dynamics
in topological spin textures
2004 Research Fellow of the Japan Society for the Promotion
of Science
2006 Project Assistant Professor, University of Tokyo
2008 Assistant Professor, University of Tokyo
Molecular beam epitaxy growth of superconducting
LiFeAs film on SrTiO3(001) substrate
2012 ASI Research Scientist, RIKEN
High-speed magnetic memories and photonic-magnonic interconnections will be
realized by using the pulsed-optical-control of spins. For this purpose, the
inverse-Faraday effect, one of the optomagnetic phenomena, is promising, where
circularly-polarized laser pulses at non-absorbing photon energy can induce effective
magnetic fields via strong spin-orbit interactions. We demonstrated that the collective
dynamics of magnetic skyrmions, topologically-protected nano-scale spin vortices, can
be characterized by using the inverse-Faraday excitation and time-resolved
magneto-optics with sub-picosecond time-resolution. We also found that magnetoelastic
waves, coupled propagation of magnon and phonon, can be excited in iron garnet films
by photoexcitation. The time-resolved microscopy on the magnetoelastic wave revealed
that this traveling spin excitation shows an attractive interaction with magnetic bubbles
(skyrmions) and domain walls, whose efficiency strongly depends on the curvature of the
local spin texture.
(a) Schematics for the impulsive
Raman excitation.
(b) Rotation dynamics of magnetic
skyrmions in Cu2OSeO3.
(c) Magneto-optical microscopy on
photoexcited magnetoelastic waves.
(d) Optical manipulation of a
magnetic bubble domain.
Publications
Publications
40
2013 Senior Research Scientist, RIKEN Center for Emergent
Matter Science
2015 Unit Leader, Emergent Photodynamics Research Unit,
Outline
Our research unit explores novel photodynamics of
electron/spin in bulk crystals and at thin-film interfaces
emerging via electron-correlation and strong spin-orbit
interactions. Examples are the spin current generation
mediated by photoexcited Dirac electrons and the
ultrafast coherent control/spectroscopy of topological
spin textures. With a strong command of photons, we
try to realize new photomagnetic effects in solids, and
visualize the spatiotemporal propagation of elementally
excitations at the sub-diffraction limit.
The stoichiometric “111” iron-based superconductor, LiFeAs, has attacted great
research interest in recent years. For the first time, we have successfully grown a LiFeAs
thin film by molecular beam epitaxy on a SrTiO3(001) substrate, and studied the interfacial
growth behavior by reflection high-energy electron diffraction and low-temperature
scanning tunneling microscope. The effects of substrate temperature and Li/Fe flux ratio
were investigated. A uniform LiFeAs film as thin as 3 quintuple layers (QL) is formed. A
2008 Ph.D., Institute of Physics, Chinese Academy of
Sciences, Beijing, China.
2008 Postdoctoral Fellow, IBM T. J. Watson Research Center,
NY, USA
2011 Postdoctoral Fellow, Columbia University, NY, USA
2012 Assistant Professor, Department of Physics, Tsinghua
University (-present)
2014 Unit Leader, Quantum Surface and Interface Research
RIKEN Center for Emergent Matter Science(-present)
Outline
superconducting gap appears in LiFeAs films thicker than 4QL at 4.7K. When the film is
thicker than 13QL, the superconducting gap determined by the distance between the
coherence peaks is about 7meV, close to the value of bulk material. The ex situ transport
measurement of a thick LiFeAs film shows a sharp superconducting transition around
16K. The upper critical field, Hc2(0)=13.0T, is estimated from the temperature-dependent
magnetoresistance. The precise thickness and quality control of the LiFeAs film paves the
road for growing similar ultrathin iron
arsenide films.
MBE growth of LiFeAs film. (a) The tetragonal
structure of LiFeAs. (b) RHEED pattern of the (001)
surface of the SrTiO3 substrate, which shows the
2×2 reconstruction. The arrows indicate the 1×1
stripes. (c), (d): RHEED patterns of a LiFeAs thin
film on the SrTiO3 substrate after 8 (c) and 60 (d)
minutes deposition. The weak spots marked by the
arrows show the formation of a small amount of
Li3As clusters on the surface during growth. (e), (f):
STM topographic images of SrTiO3(001) (e) and
25QL LiFeAs film (f). Image size: 500 nm × 250
nm; sample bias: 1.0V; tunneling current: 100 pA.
(g) Atomically resolved STM topography image on
the surface of a 25QL LiFeAs film (10 nm×10nm,
8.0mV, 2.0nA). (h) The evolution of the in-plane
lattice constant ain-plane determined by RHEED
as a function of the film thickness. (i) ThedI/dV
Publications
spectrum on the surface of a 13QL LiFeAs film. Our research unit focuses on the emergent
phenomena on the surface/interface of the newly
discovered topological related quantum materials,
such as topological insulators and topological
crystalline insulators. We are interested in the
fundamental properties of those symmetry protected
surface states. In particular, we are interested in
topological surface states with the gap opening
induced by the time reversal symmetry breaking, or
gauge symmetry breaking, or interaction of two
surface states through tunneling effect, which could
lead to the exotic phenomena, such as surface
quantum hall effect, topological magnetoelectric effect
and topological superconducting.
Publications
1. N. Ogawa, W. Koshibae, A. J. Beekman, N. Nagaosa, M. Kubota, M. Kawasaki, and Y. Tokura,
“Photo-drive of magnetic bubbles via magnetoelastic waves”, Proc. Natl. Acad. Sci. 112, 8977 (2015).
1. K. Chang, P. Deng, T. Zhang, et al., “Molecular beam epitaxy growth of superconducting LiFeAs film on
SrTiO3(001) substrate”, Europhys. Lett., 109, 28003 (2015).
2. N. Ogawa, S. Seki, and Y. Tokura, “Ultrafast optical excitation of magnetic skyrmions”, Sci. Rep. 5, 9552
(2015).
2. S.-H. Ji, J. B. Hannon., R. M. Tromp, et al., “Atomic scale transport of epitaxial graphene”, Nat. Mater.,
11,114 (2012).
3. N. Ogawa, M. S. Bahramy, Y. Kaneko, Y. Tokura, “Photocontrol of Dirac electrons in a Rashba
semiconductor”, Phys. Rev. B 90, 125122 (2014).
3. S.-H. Ji, T. Zhang, Y.-S. Fu, et al., “Application of magnetic atom induced bound states in superconducting
gap for chemical identification of single magnetic atoms”, Appl. Phys. Lett., 96, 073113 (2010).
4. N. Ogawa, M. S. Bahramy, H. Murakawa, Y. Kaneko, and Y. Tokura, “Magnetophotocurrent in BiTeI with
Rashba spin-split bands”, Phys. Rev. B 88, 035130 (2013).
4. X. Chen, Y.-S. Fu, S.-H. Ji, et al., “Probing superexchange interaction in molecular magnets by spin-flip
spectroscopy and microscopy”, Phys. Rev. Lett., 101, 197208 (2008).
5. N. Ogawa, Y. Ogimoto, Y. Ida, Y. Nomura, R. Arita, and K. Miyano, “Polar antiferromagnets produced with
orbital-order”, Phys. Rev. Lett. 108, 157603 (2012).
5. S.-H. Ji, Y.-S. Fu, X. Chen, et al., “High-resolution scanning tunneling spectroscopy of magnetic-impurity-induced
bound states in the superconducting gap of Pb thin-films”, Phys. Rev. Lett., 100, 226801 (2008).
41
Cross-Correlated Interface Research Unit
Computational Materials Function Research Unit
Pu Yu (Ph.D.), Unit Leader
Yong Xu (Ph.D.), Unit Leader
yupu＠riken.jp
yong.xu＠riken.jp
Research field
Research field
Condensed Matter Physics, Materials Science
Keywords
Keywords
Multiferroics, Interface electronic structure,
Magnetoelectric effect, Thin films and interfaces
First-principles calculations, Topological quantum
matters, Thermoelectric effect, Thin films and
interfaces, Theoretical materials design
Brief resume
Brief resume
2011 Ph.D in Physics, University of California, Berkeley, USA
Interface control of bulk properties
Typically, the interface effect is highly localized within a few unit cells from the interface.
However, it can propagate through the whole layer if one of the layers is ferroic
(ferromagnetic or ferroelectric) in nature. Using a model system consisting of the
f e r ro m a g n e t L a 0.7 S r 0.3 M n O 3 ( L S M O ) a n d t h e m u l t i f e r ro i c ( f e r ro e l e c t r i c a n d
2012 Assistant Professor, Tsinghua University, Beijing, China
(-present)
2014 Unit Leader, Cross-Correlated Interface Research Unit,
Outline
Discovery of graphene’s latest cousin: stanene
One of the grand challenges in condensed matter physics and material science is to
develop room-temperature electron conduction without dissipation. Based on first-principles calculations, we predicted a new material class of stanene (i.e., the latest cousin of
graphene) that is promising for the purpose. Stanene (from the Latin stannum meaning
antiferromagnetic) BiFeO3 (BFO), we demonstrated that the interfacial valence mismatch
tin) is a 2D layer of tin atoms in a buckled honeycomb lattice. One intriguing feature of
between BFO and LSMO layers can be employed to influence the electrostatic potential
stanene and its derivatives is that the materials support large-gap quantum spin Hall
step across interfaces and control the ferroelectric state of BFO layer. One the other
(QSH) states, enabling conducting electricity without heat loss. Moreover, many other
hand, the novel ferromagnetic state formed at the BFO interface sublattice is responsible
exotic characteristics were also proposed theoretically for stanene-related materials,
for the existence of exchange bias
including enhanced thermoelectric performance, topological superconductivity and the
coupling across the interface. Furthermore,
near-room-temperature quantum anomalous Hall effect. Very recently we have success-
the interplay between charge and spin
fully fabricated the monolayer stanene structure by molecular beam epitaxy. This will stim-
degrees of freedom across the interface
ulate great experimental effort to observe the unusual electronic properties of stanene.
can lead to a reversible switch/control
between two distinct exchange bias states
by isothermally switching the ferroelectric
polarization of BFO layer. These results
suggest a novel pathway to design the
bulk properties through the heterointerface
engineering.
Schematic drawing of interface coupling strength
through heterointerfaces. In regular materials, the
influence of interface coupling is mainly limited to the
interface. While for the materials with long-range
spontaneous orders, the interface coupling can
propagate all the way through the bulk material.
Publications
1.Publications
J. C. Yang, Q. He, P. Yu, and Y. H. Chu, “BiFeO3 Thin Films: A Playground for Exploring Electric-Field
Control of Multifunctionalities”, Annu. Rev. Mater. Res., 45, 3.1 (2015).
2. D. Yi, J. Liu, O. Satoshi, S. Jagannatha, Y. C. Chen, P. Yu, Y. H. Chu, E. Arenholz, and R. Ramesh, “Tuning
the competition between ferromagnetism and antiferromagnetism in a half doped manganite through
magnetoelectric coupling”, Phys. Rev. Lett., 111, 127601 (2013).
42
2012 Postdoctoral Researcher, Correlated Electron Research
Group, RIKEN, Japan
Our research unit is dedicated to exploring the
emergent phenomena at complex oxide and other
cross-correlated heterostructures and interfaces. In
p a r t i c u l a r, w e a re i n t e re s t e d a b o u t q u a n t u m
manipulation of ferroelectric and ferromagnetic
properties by means of heteroepitaxy, artificial design
of novel multiferroic materials with strong
magnetoelectric coupling and emergent phenomena
(with a strong focus on the spin and charge degrees of
freedom) at complex oxide interfaces and their cross
correlations to other correlated material systems. Our
goal is to reveal the underlying mechanisms of these
heretofore-unexplored functionalities, and transfer
them into novel device concepts for applications.
Core members
(Student Trainee) Jingwen Guo, Shuzhen Yang
2010 Ph.D., Condensed Matter Physics, Tsinghua University,
Beijing, China
2013 Alexander von Humboldt Fellow, Fritz Haber Institute,
Berlin, Germany
2015 Research Scholar, Stanford University, USA
2015 Assistant Professor, Tsinghua University, Beijing, China
(-present)
2015 Unit Leader, Computational Materials Function Research
Outline
We a re a re s e a rc h g ro u p o n t h e o re t i c a l a n d
computational condensed-matter and materials
physics. Our main research interest is to
understand/predict unusual quantum phenomena and
novel material properties, based on first-principles
electronic structure calculations. In particular, we focus
on exploring the electronic, thermal, optical and
magnetic properties of low-dimensional systems (e.g.
layered materials, materials surfaces and interfaces) as
well as materials with non-trivial topological order. The
primary goal of our research is to design advanced
functional materials that can be used for
low-dissipation electronics, high-performance
thermoelectricity and high-efficiency solar cell. We are
also interested in developing theoretical methods for
studying quantum thermal, electronic, and
thermoelectric transport at the mesoscopic scale.
(a) An element familiar as the coating for tin cans: tin (chemical symbol Sn).
(b) A 2D layer of tin, named stanene, when decorated by halogen atoms, is able to conduct
electricity perfectly along its edges (blue and red arrows) at room temperature.
(c) The atomic structure model (top view) superimposed on the measured STM images for the
Publications
2D stanene on Bi2Te3(111). (d) Side view.
Publications
1. F. Zhu, W.-J. Chen, Y. Xu, C.-L. Gao, D.-D. Guan, C. Liu, D. Qian, S.-C. Zhang, and J.-F. Jia, "Epitaxial
Growth of Two-Dimensional Stanene", Nat Mater. Published online (doi:10.1038/nmat4384) (2015).
3. M. Huijben, P. Yu, L. W. Martin, H. J. A. Molegraaf, Y. H. Chu, M. B. Holcomb, N. Balke, G. Rijnders, and
R. Ramesh, “Ultrathin limit of exchange bias coupling at oxide multiferroic/ferromagnetic interface”, Adv.
Mater., 25, 4739 (2013).
2. Y. Xu, Z. Gan, and S.-C. Zhang, "Enhanced Thermoelectric Performance and Anomalous Seebeck Effects
in Topological Insulators", Phys. Rev. Lett. 112, 226801 (2014).
4. P. Yu, Y. H. Chu, and R. Ramesh, “Oxide Interfaces: Pathways to Novel Phenomena”, Materials Today, 15,
320 (2012).
4. Y. Xu, B. Yan, H.-J. Zhang, J. Wang, G. Xu, P. Tang, and W. Duan, S.-C. Zhang, "Large-gap quantum spin
Hall insulators in tin films", Phys. Rev. Lett. 111, 136804 (2013).
5. P. Yu, W. Luo, D. Yi, J. X. Zhang, M. D. Rossell, C. H. Yang, L. You, G. Singh-Bhalla, S. Y. Yang, Q. He, Q.
M. Ramasse, R. Erni, L. W. Martin, Y. H. Chu, S. T. Pantelides, S. J. Pennycook, and R. Ramesh, “Interface
control of bulk ferroelectric polarization”, Proc. Natl. Acad. Sci. USA, 109, 9710-9715 (2012).
5. Y. Xu, O. T. Hofmann, R. Schlesinger, S. Winkler, J. Frisch, J. Niederhausen, A. Vollmer, S. Blumstengel, F.
Henneberger, N. Koch, P. Rinke, and M. Scheffler, "Space-charge transfer in hybrid inorganic/organic
systems", Phys. Rev. Lett. 111, 226802 (2013).
3. Y. Xu, Z. Li, and W. Duan, "Thermal and Thermoelectric Properties of Graphene", Small 10, 2182 (2014).
43
Emergent Superstructure Research Unit
Emergent Computational Physics Research Unit
Yuichi Yamasaki (D. Eng), Unit Leader
Mohammad Saeed Bahramy
yuichi.yamasaki@riken.jp
(D. Eng.), Unit Leader
bahramy@riken.jp
Research field
Research field
Keywords
Keywords
X-ray scattering, Structure Science, Spectroscopy,
Imaging, Skyrmion
Topological quantum matters, Surface and
heterogeneous interfaces, Oxides, Spintronics,
Valleytronics, Thermoelectric effect, Strongly
correlated electron system, First-principles calculations
Brief resume
2009 D. Eng., University of Tokyo
Skyrmion Crystal as Probed by
Small-Angle Resonant Soft X-ray Scattering
Dzyaloshinskii-Moriya interaction due to the breaking of inversion symmetry in crystal
lattice occasionally induces a topological spin texture in a ferromagnet, known as a magnetic skyrmion. The nano-scale skyrmions, as topologically protected, have high potential
for novel spintronic applications. We investigate the formation and dynamics of skyrmion
crystal, i.e. the triangular lattice of skyrmions, by means of resonant small angle x-ray
scattering, a useful method to detect the magnetic order in 3d-transition metal compounds with use of core excitations from the transition-metal 2p to the 3d states. The
coherent soft x-ray scattering is capable of reconstructing a real-space image of magnetic
moment distribution and may also offer the opportunity for time-resolved measurements
of fast skyrmion crystal dynamics under applied external field.
2009 Research Associate, Institute of Materials Structure
Science, High Energy Accelerator Research
Organization
2014 Project Lecturer, Quantum-Phase Electronics Center,
University of Tokyo (-present)
2014 Unit Leader, Emergent Superstructure Research Unit,
RIKEN Center for Emergent Matter Science (-present),
Outline
In strongly correlated electron system, orderings of
electronic degrees of freedom, such as charge, spin
and orbital, show various intriguing emergent phenomena and functionalities, such as magneto-electric
multiferroics. We investigate the spatial modulation of
electronic state by synchrotron x-ray- and neutrondiffraction and spectroscopic study for understanding
these phenomena. We also aim to develop novel resonant x-ray diffraction measuring techniques to discover new emergent phenomena in strongly correlated
electron system.
Modeling emergent quantum confinement
phenomena from first-principles
Two-dimensional electron gases (2DEGs) formed at the surface/interface of complex
systems such as topological insulators and transition metal oxides offer an ideal
playground to search for the exotic states of quantum matter. Unfortunately, the available
theoretical models are often too oversimplified−or otherwise dependent on too many
adjustable parameters− to provide a unified picture of the underlying mechanisms in
these 2DEG systems. To address this issue, we have developed a sophisticated
computational technique, which can accurately describe the electronic structure of 2DEG
systems under realistic conditions. Our approach is essentially parameter-free, as it relies
on the solution of coupled Schrödinger-Poisson equation with input parameters taken
have applied our method to a variety of 2DEG
Through these studies, we have uncovered how
quantum confinement, inversion symmetry
breaking and topology of bulk bands collectively
tune the delicate interplay of charge, spin, orbital
and lattice degrees of freedom in these systems.
Our method allows for a unified understanding
of spectroscopic and transport measurements
across different classes of 2DEGs, and yields
new microscopic insights on their functional
1. Y. Yamasaki, H. Nakao, Y. Murakami, T. Nakajima, A. L. Sampietro, H. Ohsumi, M. Takata, T. Arima, and Y.
Tokura, “X-ray induced lock-in transition of cycloidal magnetic order in a multiferroic perovskite manganite”,
Phys. Rev. B, 91, 100403 (R) (2015).
2. J. Fujioka, Y. Yamasaki, H. Nakao, R. Kumai, Y. Murakami, M. Nakamura, M. Kawasaki, and Y. Tokura,
“Spin-orbital superstructure in strained ferrimagnetic per ovskite cobalt oxide”, Phys. Rev. Lett., 111,
027206 (2013).
3. Y. Yamasaki, H. Sagayama, N. Abe, T. Arima, K. Sasai, M. Matsuura, K. Hirota, D. Okuyama, Y. Noda, and
Y. Tokura, “Cycloidal Spin Order in the a-axis Polarized Ferroelectric Phase of Orthorhombic Perovskite
Manganite”, Phys. Rev. Lett., 101, 097204 (2008).
4. Y. Yamasaki, H. Sagayama, T. Goto, M. Matsuura, K. Hirota, T. Arima, and Y. Tokura , “Electric Control of
Spin Helicity in a Magnetic Ferroelectric”, Phys. Rev. Lett., 98, 147204 (2007).
5. Y. Yamasaki, S. Miyasaka, Y. Kaneko, J.-P. He, T. Arima, and Y. Tokura, “Magnetic Reversal of the
Ferroelectric Polarization in a Multiferroic Spinel Oxide”, Phys. Rev. Lett., 207204 (2006).
44
2007 Postdoctoral Researcher, Institute for Materials
Research, Department of Materials Science and
Engineering, Tohoku University
2008 JSPS Postdoctoral Researcher, Institute for Materials
Research, Department of Materials Science and
Engineering, Tohoku University
2010 Postdoctoral Researcher, Correlated Electron Research
Group, Advanced Science Institute, RIKEN
2013 Research Scientist, Strong Correlation Theory Research
Group, RIKEN Center for Emergent Matter Science
2013 Lecturer, Department of Applied Physics, The University
of Tokyo (-present)
2014 Unit Leader, Emergent Computational Physics Research
Unit, RIKEN Center for Emergent Matter Science
(-present)
Outline
systems, including those formed at the surface
s e m i c o n d u c t o r s a n d p e ro v s k i t e o x i d e s .
Publications
Publications
2007 PhD, Institute for Materials Research, Department of
Materials Science and Engineering, Tohoku University
from the first-principles bulk calculations. We
of topological insulators, bulk Rashba
Helical magnetic structure and magnetic skyrmion crystal as probed
by small-angle resonant soft x-ray scattering.
Brief resume
properties.
Hierarchy and interplay of underlying
degrees of freedom (DOFs) in SrTiO3
two-dimensional electron gas.
We focus on the study of exotic states of quantum
matter by means of the first-principles methods of
computational electronic-structure theory. We are
particularly interested in studies of topological
phenomena in strongly spin-orbit coupled systems,
emergent phenomena at the interface of
heterogeneous materials systems, thermopower
generation and manipulation in low-dimensional
systems, strongly correlated electron systems, and
superconductivity. The primary goal of our research is
to theoretically predict new physical phenomena in
these systems and design materials with advanced
electronic and magnetic functionalities. We are also
interested in the development of new theoretical
approaches and computational techniques to extend
the reach and power of the available first-principles
methods.
Publications
1. P. D. C. King, S. MacKeown, A. Tamai, A. de la Torre, T. Eknapakul, P. Buaphet, S. -K. Mo, W. Meevasana,
M. S. Bahramy, and F. Baumberger, “Quasiparticle dynamics and spin-orbital texture of the SrTiO3
Publications
two-dimensional electron gas”, Nat. Commun., 5, 3414 (2014).
2. P.-H. Chang, M. S. Bahramy, N. Nagaosa, and B. K. Nikolic, “Giant thermoelectric effect in graphene-based
topological insulators with heavy adatoms and nanopores”, Nano Lett.,14, 3779-3778 (2014).
3. H. Yuan, M. S. Bahramy, K. Morimoto, S. Wu, K. Nomura, B. J. Yang, H. Shoimotani, R. Suzuki, M. Toh,
C. Kloc, X. Xu, R. Arita, N. Nagaosa, and Y. Iwasa, “Zeeman-type spin splitting controlled by an electric
field”, Nat. Phys., 9, 563 (2013).
4. M. S. Bahramy, P. D. C. King, A. de la Torre, J. Chang, M. Shi, L. Patthey, G. Balakrishnan, Ph. Hofmann,
R. Arita, N. Nagaosa, and F. Baumberger, “Emergent quantum confinement at topological insulator
surfaces”, Nat. Commun., 3, 1159 (2012).
5. M. S. Bahramy, B. -J. Yang, R. Arita, and N. Nagaosa, “Emergence of non-centrosymmetric topological
insulating phase in BiTeI under pressure”, Nat. Commun., 3, 679 (2012).
6. M. S. Bahramy, R. Arita, and N. Nagaosa, “Origin of giant bulk Rashba splitting: Application to BiTeI”, Phys
Rev. B, 84, 041202(R) (2011).
45
Memo
Emergent Spectroscopy Research Unit
Youtarou Takahashi (Ph.D.), Unit Leader
youtarou.takahashi@riken.jp
Research field
Physics, Material science
Keywords
Strongly correlated electron system, Multiferroics,
Terahertz spectroscopy, Ultrafast spectroscopy
Brief resume
2007 Ph.D, The University of Tokyo
Magnetoelectric optical effect with
electromagnons in helimagnet
Multiferroics, in which the magnetic and the dielectric properties of matter are strongly
coupled with each other, has been attracting much attention because of the discovery of
the ferroelectricity driven by the particular spin orders. Although the light is composed of
the oscillating electric and magnetic field, one of them is responsible for the optical
2007 Researcher, Tokura Multiferroic Project, ERATO, Japan
Science and Technology Agency
2011 Lecturer, Quantum-Phase Electronics Center, School of
Engineering, The University of Tokyo
2014 Associate Professor, Quantum-Phase Electronics Center,
School of Engineering, The University of Tokyo (-present)
2014 Unit Leader, Emergent Spectroscopy Research Unit,
RIKEN Center for Emergent Matter Science(-present)
Outline
response in general. Since the multiferroics exhibits the cross-coupled character, such
materials has been expected to possess the composite excitation of the magnetic and
the dielectric responses. We demonstrated the ubiquitous presence of the magnetoelectric resonance with electromagnons, which is magnon excitation endowed with the electric transition dipole moment, in helimagnet. The electromagnon always shows the optical magnetoelectric effect, which can be observed as the nonreciprocal directional dichroism, in which the optical response changes with the reversal of the propagation vector of
light. We observed gigantic optical magnetoelectric effect on the resonance of the electromagnon, as large as 1 in the imaginary part of the refractive index.
Optical spectroscopy is a useful tool for the comprehensive study of the materials, while the sophisticated
control of the matter enables us a development of new
optical responses. Our team focuses on the optical
process in the strongly correlated electron systems for
the clarification of the dynamics of matter and for the
explorations of the new optical phenomena. By using
the laser spectroscopy, we study (1) the magnetoelectric optical effect driven by the cross-coupling
between the magnetism and dielectric properties in
matter, (2) optical control of the magnetism and dielectric properties and (3) the dynamical character of the
conduction electron, leading to the novel optics and
the possible applications.
Electromagnon is active for both electric and magnetic field of the light,
Publications results in the directional dichroism.
Publications
1. S. Kibayashi, Y. Takahashi, S. Seki, and Y. Tokura, “Magnetochiral dichroism resonant with electromagnons
in a helimagnet”, Nat. commun., 5, 4583 (2014).
2. Y. Takahashi, S. Chakraverty, M. Kawasaki, H. Y. Hwang, and Y. Tokura,“In-plane terahertz response of thin
film Sr2RuO4”, Phys. Rev. B, 89, 165116 (2014).
3. K. Ueda, J. Fujioka, Y. Takahashi, T. Suzuki, S. Ishiwata, Y. Taguchi, M. Kawasaki, and Y. Tokura,
“Anomalous domain-wall conductance in Pyrochlore-type Nd2Ir2O7 on the verge of metal-insulator
transition”, Phys. Rev. B, 89, 075127 (2014).
4. Y. Takahashi, Y. Yamasaki, and Y. Tokura, “Terahertz Magnetoelectric Resonance Enhanced by Mutual
Coupling of Electromagnons”, Phys. Rev. Lett.,111.037204 (2013).
5. Y. Takahashi, R. Shimano, Y. Kaneko, H. Murakawa, and Y. Tokura, “Magnetoelectric resonance with
electromagnon in a perovskite helimagnet”, Nat. Phys., 8, 121 (2012).
46
47
Index
M
A
Artificial atoms
Atomic physics
Computational Quantum Matter R.T. (S. Yunoki)
Superconducting Quantum Simulation R.T. (J. Tsai) 35
Magnetocaloric effect
Quantum Condensed Matter R.G. (F. Nori)
Magnetoelectric effect
25
25
B
Berry phase physics
Strong Correlation Physics R.G. (Y. Tokura)
Biomimetics
Emergent Soft Matter Function R.G. (T. Aida)
16
Emergent Bioinspired Soft Matter R.T. (Y. Ishida)
18
Quantum Condensate R.T. (M. Ueda)
26
Bose-Einstein condensation
6
Carbon nanotube
Quantum Effect Device R.T. (K. Ishibashi)
33
Chemical analysis
Materials Characterization S.U. (D. Hashizume)
23
Cold atoms
26
Quantum Many-Body Dynamics R.U. (T. Fukuhara) 39
Strong Correlation Materials R.T. (Y. Taguchi)
9
Quantum computing
Quantum Functional System R.G. (S. Tarucha)
24
Strong Correlation Theory R.G. (N. Nagaosa)
7
Quantum Condensed Phases R.T. (K. Kono)
34
6
Strong Correlation Interface R.G. (M. Kawasaki)
8
9
Strong Correlation Quantum Transport R.T. (Y. Tokura) 10
Strongly correlated electron system
42
Quantum correlations
Superconducting Quantum Electronics R.T. (Y. Nakamura) 27
30
Quantum devices
8
First-Principles Materials Science R.T. (R. Arita)
15
Quantum dots
24
Emergent Spintronics R.U. (S. Seki)
36
Materials science at high electric field
26
14
Emergent Device R.T. (Y. Iwasa)
19
Quantum System Theory R.T. (D. Loss)
30
Dynamic Emergent Phenomena R.U. (F. Kagawa)
37
Metamaterial
Spin Physics Theory R.T. (G. Tatara)
31
33
Emergent Photodynamics R.U. (N. Ogawa)
40
Microwave
Quantum information
34
Quantum information processing Quantum Condensed Matter R.G. (F. Nori)
25
Molecular design
16
Quantum optics
25
Emergent Bioengineering Materials R.T. (Y. Ito)
22
Quantum relay
31
Quantum simulation
Molecular evolutionary engineering
14
Monopole
25
Multiferroics
31
E
Emergent Computational Physics R.U. (M. S. Bahramy) 45
Emergent Spectroscopy R.U. (Y. Takahashi)
Strong Correlation Quantum Structure R.T. (T. Arima) 11
Emergent Superstructure R.U. (Y. Yamasaki)
44
24
Superconducting qubits
25
24
Superconductivity
26
6
9
46
Structure science
7
Emergent Phenomena Measurement R.T. (T. Hanaguri) 12
14
19
36
Qubit
Cross-Correlated Interface R.U. (P. Yu)
42
R
46
RKKY interaction in low dimensions Quantum System Theory R.T. (D. Loss)
Education of users
Emergent Matter Science R.S.T. (H. Akimoto)
32
Electron correlation
Quantum Matter Theory R.T. (A. Furusaki)
13
Electron diffraction
Nanobiotechnology
22
Sample characterization
32
Electron holography
Emergent Phenomena Observation Technology R.T. (D. Shindo) 28
Nanodevices
24
Scanning probe microscopy
37
Electron microscopy
Materials Characterization S.U. (D. Hashizume)
33
Scanning tunneling microscopy
34
Quantum Surface and Interface R.U. (S. Ji)
41
T
Electronic material
16
Self-assembly
16
Terahertz spectroscopy
46
Emergent electromagnetism
7
18
Theoretical materials design
15
Energy conversion
16
Nanometer scale fabrication
32
Emergent Functional Polymers R.T. (K. Tajima)
21
Computational Materials Function R.U. (Y. Xu)
43
22
Nanostructure control
21
Semiconducting polymers
Emergent Molecular Function R.G. (K. Takimiya)
17
Thermoelectric effect
16
Neutron scattering
Semiconductor nanowire
33
19
Sensors
22
43
Skyrmion
N
23
Environmentally friendly material Emergent Soft Matter Function R.G. (T. Aida)
18
F
Nanomagnetism
30
29
O
Optical lattice
26
Superfluidity
S
Quantum Nano-Scale Magnetism R.T. (Y. Otani)
34
Surface and heterogeneous interfaces
41
6
9
Thin films and interfaces
Field effect transistor
19
9
First-principles calculations
15
Optical properties
Physicochemical Soft Matter R.U. (F. Araoka)
38
44
43
Organic electronics
Emergent Soft System R.T. (T. Someya)
20
16
42
21
18
43
37
Soft-matter physics
38
38
Spectroscopy
37
17
44
20
Spin accumulation
29
Organic light emitting devices
20
Spin control
24
Organic nonlinear optics
38
Spin current
29
41
Organic semiconductor
17
31
43
Organic sensors
20
Organic solar cells
17
20
21
8
Flux quantum
Frustrated quantum magnets Quantum Matter Theory R.T. (A. Furusaki)
Organic ferroelectrics
13
Organic field-effect transistor
High pressure synthesis
9
High-temperature superconductor
I
Imaging
44
Interface electronic structure Strong Correlation Quantum Transport R.T. (Y. Tokura) 10
Interface electrons
42
Josephson effect
Oxides
7
J
38
Low dimensional superconductors
41
Spin Hall effect
29
Spin-orbit interaction
Topological superconductivity Quantum Matter Theory R.T. (A. Furusaki)
30
6
8
41
6
13
30
Two-dimensional electron system Emergent Device R.T. (Y. Iwasa)
13
19
34
40
46
U
Ultrafast spectroscopy
31
Photoelectric conversion material
40
V
Spintronics
Quantum Matter Theory R.T. (A. Furusaki)
16
Topological quantum matters Quantum System Theory R.T. (D. Loss)
7
Spin-based quantum information science
Topological insulators
P
Liquid crystals, polymeric materials
Soft material
29
Valleytronics
Photovoltaic effect
8
31
X
Pi-electronic compound
17
36
X-ray crystal structure analysis Materials Characterization S.U. (D. Hashizume)
Polymer synthesis
21
40
X-ray scattering
Precise polymer synthesis
22
L
48
18
D
Domain wall
16
Quantum coherence
Majorana fermions and parafermions
Computational condensed matter physics
Condensed matter physics
14
C
Stimuli-responsive material
Q
Magnetism
23
44
49
October 1, 2015 ©RIKEN CEMS, All Rights Reserved

Outline of Center for Emergent Matter Science

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