Symmetries and Interactions in Topological Matter

Transcription

WILLIAM I. FINE THEORETICAL PHYSICS INSTITUTE
May 1st - May 3rd 2015
TABLE OF CONTENTS
Program..........................................................................................2
Workshop Banquet info..........................................................4 & 25
Abstracts.........................................................................................9
Wireless Information.....................................................................20
Participant List...............................................................................21
Talk Uploading Instructions..........................................................26
Maps
Workshop Banquet Location................................................25 Dining Guide........................................................................27
Additional Locations............................................................28
Poster Presentation List.................................................................29
William I. Fine Theoretical Physics Institute
School of Physics & Astronomy
University of Minnesota
116 Church Street SE
Minneapolis, MN 55455
Phone: (612) 624-7366
Fax: (612) 626-8606
ftpi@physics.umn.edu
www.ftpi.umn.edu
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Welcome to the
workshop
We are delighted to host the workshop, “Symmetries and Interactions in Topological Matter,”
sponsored by the William I. Fine Theoretical Physics Institute (FTPI), at the University of
Minnesota. This exciting event will be held in Minneapolis from the morning of Friday, May 1st,
to the afternoon of Sunday, May 3rd, 2015. We will host a workshop dinner on Friday, May 1st and
a poster session in the afternoon on Saturday, May 2nd.
Scientific Organizing Committee:
Andrei Bernevig, Princeton University
Fiona Burnell, University of Minnesota
Alex Kamenev, University of Minnesota, FTPI
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FRIDAY, MAY 1ST
The Commons Hotel, Ballroom 2nd floor
8:40 amREGISTRATION
The Commons Hotel – Ballroom
2nd floor - to the right at the top of the escalators
8:55 am Welcome and opening comments
Alex Kamenev
9:00 am
Symmetry Protected Topological Semimetals
Charles Kane
University of Pennsylvania
9:35 am
Evidence for the chiral anomaly in a Dirac semimetal
N.P. Ong
Princeton University
10:10 am
COFFEE BREAK
10:45 am
Effective field theory of the disordered Weyl semimetal
Alexander Altland
University of Cologne
11:20 am
2D Topo.Superconductors, Weyl Semimetals and other exotic Cooper Pairing
M. Zahid Hasan
11:55 am
Interplay between Symmetry and Geometry in Topological Phases
Taylor Hughes
University of Illinois at Urbana-Champaign
12:30 pm
LUNCH BREAK - Lunch is on your own
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FRIDAY, MAY 1ST
Keller Hall 3-180
200 Union Street SE, Minneapolis, MN
***LOCATION CHANGE - KELLER HALL 3-180***
2:00 pm
Braiding statistics and symmetry-protected topological phases
Michael Levin
University of Chicago
2:35 pm
Fractionalization of Faraday lines in generalized compact quantum electrodynamics
(CQED) and Symmetry Protected Topological phases and Symmetry Enriched Topological phases of CQED
Olexei Motrunich
California Institute of Technology
3:10 pm
Time reversal invariant gapped boundaries of the double semion state
Xie Chen
3:45 pm
COFFEE BREAK
4:15 pm
Metal-insulator transition and beyond in the pyrochlore iridates
Leon Balents
University of California, Santa Barbara
4:50 pm
Novel transport and magnetic phenomena in strongly spin-orbit coupled materials
James Analytis
University of California, Berkeley
5:25 pm
Topological Spin Liquid and Symmetry Characterization for Triangular Lattice Spin 1/2 J1-J2 model
Donna Sheng
California State University, Northridge
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FRIDAY, MAY 1ST
Keller Hall 3-180
6:00 pm
Workshop ends for the day
6:15 pm Non UMN participants - Board bus for departure at 6:30 pm to workshop dinner
Bus will pick-up outside of Keller Hall on Union Street
East side of Keller Hall
6:30 pm Bus departs for Harriet Island
7:00 pm WORKSHOP DINNER
Centennial Showboat
Harriet Island West
100 Yacht club road, St Paul MN 55107
10:00 pm
Workshop dinner ends. Bus will pick up non UMN participants and drop off at
The Commons hotel.
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SATURDAY, MAY 2ND
Keller Hall 3-180
9:00 am
Quantum criticality of 1D topological Anderson insulators
Dmitry Bagrets
9:35 am
Transport and Josephson phenomena in hybrid superconductor-topological insulator devices
Dale Van Harlingen
10:10 am
COFFEE BREAK
10:45 am
Search for additional signatures of Majorana fermions in semiconductor nanowires coupled to superconductors
Sergey Frolov
University of Pittsburgh
11:20 am
Majorana takes charge: from teleportation to quantum computation
Liang Fu
Massachusetts Institute of Technology
11:55 am
Progress in the materials science of hybrid nanowires for topological devices
Jesper Nygard
Neils Bohr Institute
12:30 pm
LUNCH BREAK - Lunch is on your own
2:00 pm
Topological Superconductivity with Magnetic Atoms
Leonid Glazman
Yale University
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SATURDAY, MAY 2ND
Keller Hall 3-180
2:35 pm
Majorana bound states in ferromagnetic atomic chains on a superconductor
Stevan Nadj-Perge
3:10 pm
Luttinger Behavior in the Ultralow Temperature Transport of InAs/GaSb Edge States
Rui-Rui Du
Rice University
3:45 pm
COFFEE BREAK
4:15 pm
Detecting topological orders in an infinite cylinder geometry
Frank Pollmann
Max Planck Dresden
4:50 pm
Light-matters: from Floquet topological insulators to topolaritons
Gil Refael
5:30 pm
POSTER SESSION
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SUNDAY, MAY 3RD
Keller Hall 3-180
9:00 am
Imaging current in quantum spin Hall insulators
Katja Nowack
Cornell University
9:35 am Topology and quantum coherence in `hot’ matter
Ashvin Vishwanath
University of California at Berkeley
10:10 am
Supercurrent in the edge modes of InAs/GaSb
Vlad Pribiag
10:45 am
COFFEE BREAK
11:15 am
Composite Dirac liquids: parent states for symmetric surface topological
order Jason Alicea
11:50 am
3d symmetry protected phases and surface topological order
Lukasz Fidkowski
Stony Brook
12:25 pm
Symmetry-protected topological phases and cross-cap states
Shinsei Ryu
1:00 pm
Workshop Closing
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SUNDAY, MAY 3RD
Keller Hall 3-180
THANK YOU FOR YOUR PARTICIPATION!!!
If you are going to the airport from the workshop location and need a
taxi please inform the workshop staff. If you will be leaving from
the hotel please make arrangements with concierge desk at the hotel
or take advantage of the light-rail.
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ABSTRACTS
(alphabetical by speaker)
Jason Alicea
Composite Dirac liquids: parent states for symmetric surface topological order
Topological phases of matter often feature boundary physics that naively seems impossible
from the viewpoint of systems in one lower dimension. In this talk I will introduce a new class
of exotic boundary states known as `composite Dirac liquids’ that can appear at a strongly
interacting surface of a 3D electronic topological insulator. Composite Dirac liquids exhibit
a gap to all charge excitations but nevertheless feature a single massless Dirac cone built
from emergent electrically neutral fermions. These states thus comprise electrical insulators
that, interestingly, retain thermal properties similar to those of the non-interacting topological
insulator surface. I will show how gapping the neutral fermions via Cooper pairing naturally
recovers symmetric non-Abelian surface topological orders captured recently in several works.
Alexander Altland
Effective field theory of the disordered Weyl semimetal
In disordered Weyl semimetals, mechanisms of topological origin lead to the|protection against
Anderson localization, and at the same time to different|types of transverse electromagnetic
response -- the anomalous Hall, and chiral|magnetic effect. In this talk, we will discuss
the|manifestation of these phenomena at length scales which are beyond the scope|of
diagrammatic perturbation theory. Specifically we show how an interplay of|symmetry
breaking and the chiral anomaly leads to a field theory containing|two types of topological
terms. Generating the unconventional response|coefficients of the system, these terms
remain largely unaffected by disorder,|i.e. information on the chirality of the system remains
visible|even at large length scales.
James Analytis
Novel transport and magnetic phenomena in strongly spin-orbit coupled materials
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Dmitry Bagrets
University of CologneUniversity of Cologne
Quantum criticality of 1D topological Anderson insulators
In my talk I will present the recent analytic theory of quantum criticality in quasi one-dimensional
topological Anderson insulators [1,2]. We describe these systems in terms of two parameters $(g,\
chi)$ representing localization and topological properties, respectively. Certain critical values of
$\chi$ (half-integer for Z classes, or zero for Z2 classes) define phase boundaries between distinct
topological sectors. Upon increasing system size, the two parameters exhibit flow similar to the
celebrated two parameter flow of the integer quantum Hall insulator. However, unlike the quantum
Hall system, an exact analytical description of the entire phase diagram can be given in terms
of the transfer-matrix solution of corresponding supersymmetric non-linear sigma-models. In Z2
classes we uncover a hidden supersymmetry, present at the quantum critical point.
[1]”Topology versus Anderson localization: Non-perturbative solutions in one dimension”, A.
Altland, D. Bagrets, and A. Kamenev, PRB 91, 085429 (2015). [2]”Quantum criticality of quasi
one-dimensional topological Anderson insulators”, A. Altland, D. Bagrets, L. Fritz, A. Kamenev,
H. Schmiedt, PRL 112, 206602 (2014).
Leon Balents
University of California, Santa Barbara
Metal-insulator transition and beyond in the pyrochlore iridates
Iridates are interesting materials in which Coulomb repulsion, kinetic energy, and spin-orbit
coupling all are comparable. In particular the latter suggests they may be good candidates to
observe topological phenomena. The pyrochlore family, with chemical formula A2Ir2O7 (A is a
trivalent rare earth), displays both magnetic ordering and a metal-insulator transition. I will discuss
theoretical and experimental studies of these materials, focusing on aspects related to topology and
correlations, highlighting recent results.
Xie Chen
Time reversal invariant gapped boundaries of the double semion state
The boundary of a fractionalized topological phase can be gapped by condensing a proper set
of bosonic quasiparticles. Interestingly, in the presence of a global symmetry, such a boundary
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can exhibit different symmetry transformation properties, depending on the details of the
condensation. In this talk, I discuss an explicit example of this kind - the double semion state
with time reversal symmetry. We find two distinct cases where the semionic excitations on the
boundary can transform either as time reversal singlets or as time reversal doublets, depending
on the coherent phase factor of the boson condensate. The existence of these two possibilities are
demonstrated using both field theory argument and exactly solvable lattice models. Furthermore,
we study the domain walls between these two types of gapped boundaries. We find that they
carry symmetry protected degeneracies and applying time reversal symmetry tunnels a semion
between them.
Rui-Rui Du
Rice University
Luttinger Behavior in the Ultralow Temperature Transport of InAs/GaSb Edge States
Tomonaga-Luttinger liquid (LL) is a theoretical model describing the ground state of a correlated
one-dimensional (1D) electronic system. Confirmations of this ground state have been examined
in various materials, such as carbon nanotubes, semiconductor nanowires, and cleaved-edgeovergrowth 1D channel, as well as fractional quantum Hall edge states, respectively for spinfull or chiral Luttinger liquids. It is theoretically proposed that in the limit of strong electronelectron interaction, the edge states of quantum spin Hall insulator (QSHI) are (spin-less) helical
Luttinger liquids (HLL). Motivated by this interesting prospect, we investigate transport of edge
states in InAs/GaSb quantum wells (QWs), which shows characteristic nonlinear conductance at
ultra-low temperatures. A unique advantage of the 1D electronic system in InAs/GaSb is that the
Luttinger parameter K can be controlled by various experimental knobs, such as gates as well as
QW parameters. As an example, here the relevant K values can be tuned between ~ 0.24 and ~
0.13 by gates. We found a scaling relation of conductance vs. eV/kBT, where eV is the voltage
bias across the edge length, kBT is the temperature.
Lukasz Fidkowski
Stony Brook
3d symmetry protected phases and surface topological order
I will consider gapped Hamiltonians of generalized spin models, which are invariant under
a certain unbroken onsite unitary symmetry group. It is well known that such Hamiltonians
can realize topologically ordered phases, which in (2+1)d can be studied with modular tensor
categories. When a symmetry is included, the corresponding `symmetry enriched’ phases
correspond to a richer mathematical structure - e.g. braided G-crossed categories in (2+1)
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d. However, in systematically constructing such braided G-crossed categories by extending
ordinary modular ones one sometimes encounters obstructions. Here we give a physical
interpretation for such obstruction, and show that the corresponding topologically ordered
theory, though it cannot be realized in 2d in a G-symmetric way, can be realized at the surface
of a 3d ‘symmetry protected’ phase. I will try to emphasize the physical interpretation of the
various mathematical concepts involved, and I will explain a specific example in detail.
Sergey Frolov
Search for additional signatures of Majorana fermions in semiconductor nanowires
coupled to superconductors
I will provide and update on the experiments in InSb nanowires coupled to superconductors.
The talk will focus on tunneling experiments and the analysis of zero-bias peaks, induced
gaps and methods of the preparation of clean transparent contacts between superconductors
and semiconductors. Near term goals include the search for the closing of the topological
superconducting gap, correlations between zero-bias features, phase diagrams of the topological
states.
Liang Fu
Majorana takes charge: from teleportation to quantum computation
Leonid Glazman
Yale University
Topological Superconductivity with Magnetic Atoms
Chains of magnetic impurities embedded in a conventional s-wave superconductor may
induce the formation of a topologically non-trivial superconducting phase. If such a phase is
formed along a chain, then its ends carry Majorana fermions. We investigate this possibility
theoretically by developing a tight-binding Bogoliubov-de Gennes description, starting from
the Shiba bound states induced by the individual magnetic impurities. While the resulting
Hamiltonian has similarities with the Kitaev model for one-dimensional spinless p-wave
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superconductors, there are also important differences, most notably the long-range (powerlaw) nature of hopping and pairing as well as the complex hopping amplitudes. We develop
an analytical theory, complemented by numerical approaches, which accounts for the electron
long-range pairing and hopping along the chain [1], inhomogeneous magnetic order in the chain
of embedded impurities or spin-orbit coupling in the host superconductor, and the possibility of
direct electron hopping between the impurity atoms [2]. This allows us to elucidate the domain
of parameters favoring the formation of a topological phase and to find the spatial structure [2,3]
of Majorana states appearing in that phase. This talk is based on joint work with F. von Oppen,
Falko Pientka, and Yang Peng. [1] Falko Pientka, Leonid I. Glazman, and Felix von Oppen,
Phys. Rev. B 88, 155420 (2013). [2] Yang Peng, Falko Pientka, Leonid I. Glazman, and Felix
von Oppen, preprint arXiv:1412.0151. [3] Falko Pientka, Leonid I. Glazman, and Felix von
Oppen, Phys. Rev. B 89, 180505(R) (2014).
M. Zahid Hasan
2D Topo.Superconductors, Weyl Semimetals and other exotic Cooper Pairing
In this talk I plan to present realization of 2D topological superconductors (TSC) with Helical
Pairing [1,2] based on a Bi-based topological material and a route to SUSY critical point and
then present our experimental discovery (and theory of TaAs) of Weyl semimetal state with
Fermi arc surface states in TaAs and other related systems [3-5]. I discuss the progress in
realizing exotic Cooper pairing in these systems. ||[1] Hasan & Kane ; RMP 82, 3045 (2010)
and Qi & Zhang, RMP 83, 1057 (2011); Fu & Kane, PRL 100, 096407 (2008).|[2] S.-Y. Xu, N.
Aldoust et al., Nature Physics 10, 943 (2014).|[3] T. Grover et.al., Science 344, 280 (2014).|[4]
S.-Y. Xu, C. Liu, S. Kushwaha et al., Science 347, 294 (2015).|[5] S.-Y. Xu, Belopolski et.al.,
arXiv:1502.03807 (2015).
Taylor Hughes
Interplay between Symmetry and Geometry in Topological Phases
In this talk I will discuss new developments that illustrate the interplay between topology,
geometry, and symmetry in topological phases of matter. I will discuss the classification of some
topological insulator/superconductor phases via their spatial symmetries and the consequences
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for topological defects such as disclinations and dislocations. Additionally, I will show how spatial
symmetries can protect quantized topological responses in topological insulator phases. If time
permits, I will discuss how interactions can generate a spatial protected topological phase in a
symmetry class which only has trivial phases in the non-interacting limit.
Charles Kane
Symmetry Protected Topological Semimetals
Michael Levin
Braiding statistics and symmetry-protected topological phases
Symmetry-protected topological (SPT) phases can be thought of as generalizations of topological
insulators. Just as topological insulators have robust boundary modes protected by time reversal
and charge conservation symmetry, SPT phases have boundary modes protected by more general
symmetries. In this talk, I will describe a method for analyzing 2D and 3D SPT phases using
braiding statistics. More specifically, I will show that 2D and 3D SPT phases can be characterized by
gauging their symmetries and studying the braiding statistics of their gauge flux excitations. The 3D
case is of particular interest as it involves a generalization of quasiparticle braiding statistics to three
dimensions.
Olexei Motrunich
Fractionalization of Faraday lines in generalized compact quantum electrodynamics (CQED)
and Symmetry Protected Topological phases and Symmetry Enriched Topological phases of
CQED
Motivated by ideas of fractionalization and topological order in bosonic models with short-range
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interactions, we consider similar phenomena in formal lattice gauge theory models, which are
models where basic constituents are quantum lines. In the first example, we show that a compact
quantum electrodynamics (CQED) can have, besides familiar Coulomb and confined phases,
additional unusual confined phases where excitations are quantum lines carrying fractions of the
elementary unit of electric field strength; specifically, we construct a model that has $N$-tupled
monopole condensation and realizes 1/N fractionalization of the quantum Faraday lines. In the
second example, we consider a system consisting of two copies of CQED in (4+1)D and engineer
condensation of bound states of monopoles (which are quantum lines in four spatial dimensions)
and U(1) electric field lines. When the bound states contain a single monopole, we find lattice
gauge theory analogs of Symmetry Protected Topological phases, while when the bound states
contain multiple monopoles, we find analogs of Symmetry-Enriched Topological phases, where
we also have fractionalization of Faraday lines. The distinct character of these “topological”
phases of quantum lines is revealed by unusual response properties and physics at a boundary of a
spatial region in such a phase.
Stevan Nadj-Perge
Majorana bound states in ferromagnetic atomic chains on a superconductor
Majorana bound states are zero-energy excitations predicted to localize at the edge of a
topological superconductor, a state of matter that can form when a ferromagnetic system is placed
in proximity to a conventional superconductor with strong spin-orbit interaction. With the goal of
realizing a one-dimensional topological superconductor, we have fabricated ferromagnetic iron
atomic chains on the surface of superconducting lead [1]. Using high-resolution spectroscopic
imaging techniques, we show that the onset of superconductivity, which partly gaps the electronic
density of states in the bulk of the chains, is accompanied by the appearance of zero-energy endstates. This spatially resolved signature provides evidence, corroborated by other observations
and theoretical modeling [2], for the formation of a topological phase and edge-bound Majorana
states in this system. Our results demonstrates that atomic chains are viable platform for future
experiments to manipulate Majorana bound states [3] and to realize other 1D and 2D topological
superconducting phases.
[1] S. Nadj-Perge, I. K. Drozdov, J. Li, H. Chen, S. Jeon, J. Seo, A. H. MacDonald, B. A.
Bernevig, and A. Yazdani, Science 346, 602 (2014). [2] Jian Li, Hua Chen, Ilya K. Drozdov, A.
Yazdani, B. Andrei Bernevig, A.H. MacDonald, Phys. Rev. B 90, 235433 (2014). [3] Jian Li,
Titus Neupert, B. Andrei Bernevig, Ali Yazdani, ArXiv:1404.4058 (2014).
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Katja Nowack
Cornell University
Imaging current in quantum spin Hall insulators
Conducting edge modes at the sample boundaries are a key feature of the quantum spin Hall (QSH)
state, which was predicted and experimentally demonstrated first in HgTe quantum wells and
more recently in InAs/GaSb quantum wells. The existence of the edge modes has been evidenced
by conductance measurements on sufficiently small devices. In this talk I will describe how we
use scanning superconducting interference device (SQUID) microscopy to directly observe and
characterize edge current in both materials. The SQUID measures the out of plane component
of the magnetic field generated by current applied to our devices. From these magnetic images,
we reconstruct the 2D current density with a spatial resolution of several microns. In HgTe and
InAs/GaSb we show that the edges of the devices carry most of the current when, and only when,
the devices are tuned into their insulating gaps, directly confirming the presence of the edge
modes. In addition to identifying the edge modes, we disentangle conduction through the edges
and the interior of a device, allowing us to study the resistance of only the edges even when
the interior becomes conductive through either gating or raising the temperature. Our analysis
suggests that the edge resistance is constant over a large temperature range implying that those
scattering mechanisms which predict a power-law or stronger temperature dependence are likely
not dominant. These results deepen the puzzle of what causes backscattering in the nominally
dissipationless edge modes.
Jesper Nygard
Neils Bohr Institute
Progress in the materials science of hybrid nanowires for topological devices
Semiconductor nanowires are a backbone in proposals for topological quantum computing based
on manipulation of Majorana quasiparticles. Experimentally, various techniques exist for synthesis
of semiconductor nanowires for quantum transport. For most applications, the fabrication method
is not important once the semiconductor growth conditions and quality have been optimised. There
are also different routes for forming heterostructures, branched geometries and other advanced
nanowire materials. However, we will here focus on a unique process that is particularly promising
for topological devices: epitaxial metal/semiconductor heterostructures based on Molecular Beam
Epitaxy. Under vacuum conditions, an aluminum shell is grown in-situ onto InAs nanowires,
leading to an epitaxially matched interface between the semiconducting core and the metal coating
that acts as a superconductor at low temperatures. The perfect superconductor-semiconductor
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interface results in proximity induced superconductivity with a hard gap. The technique is
compatible with formation of branched nanostructures and opens up for new directions in
nanowire based quantum devices, e.g. transmon qubits and topological systems.
N. Phuan Ong
Evidence for the chiral anomaly in a Dirac semimetal
After an introduction to Weyl metals and the chiral anomaly, I will discuss recent transport
results showing evidence for the chiral anomaly in the Dirac semimetal Na3Bi. At low
temperature, we detect a large conductivity enhancement when the magnetic field is aligned with
the current. The enhanced conductivity corresponds to a collimated current plume that can be
steered by the magnetic field. The importance of this field locking feature as a signature of the
chiral anomaly is emphasized.|*With Jun Xiong, S. Kushwaha, Tian Liang, Wudi Wang, and R.
J. Cava
Frank Pollmann
Max Planck Dresden
Detecting topological orders in an infinite cylinder geometry
I will show that numerical investigations of a many-body ground state wavefunction using
the density matrix renormalization group (DMRG) method can yield a remarkably complete
characterization of different types of topological orders. A central tool is the entanglement
which encodes many of the essential features. First, I will show how characteristic properties of
the topological excitations in fractional quantum Hall states can be extracted directly from the
ground state wave function. Second, I will consider symmetry protected topological phases for
which the characterizing symmetry fractionalization can be determined.
Vlad Pribiag
Supercurrent in the edge modes of InAs/GaSb
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Gil Refael
Light-matters: from Floquet topological insulators to topolaritons
In my talk I will discuss how the interaction of light and matter could result in topological
behavior. I will first recount the principals behind the Floquet topological insulator in periodically
driven systems, and present fresh results on the steady states we expect in Floquet systems. I
will then show how topological phenomena emerges even without an external periodic drive
in the excitation spectrum of otherwise trivial semiconductors. In particular, I will explain how
toconstruct topological polaritons (so-called topolaritons) and topological excitons could be
observed in garden-variety solid state systems.
Shinsei Ryu
Symmetry-protected topological phases and cross-cap states
In this talk, I plan to discuss phases of matter with reflection symmetry (parity symmetry) with
interactions. While a systematic analysis is possible for non-interacting fermions, an important
challenge is to understand the effects of strong electron correlations. To get some insight into
this problem, I will discuss an example where by the effects of interactions the non-interacting
classification breaks down. I will also propose a generalization of Laughlin’s thought experiment,
a theoretical method which is powerful enough to diagnose topological phases with U(1)
symmetry but no other symmetries, to the cases of various symmetry protected topological phases.
For the case of parity symmetry, the proposed generalization consists of putting they boundary
theories of a SPT phase on an unoriented surfaces, and hence is related to the so-called orientifold
quantum field theories.
Donna Sheng
California State University, Northridge
Topological Spin Liquid and Symmetry Characterization for Triangular Lattice
Spin 1/2 J1-J2 model
We study the spin-1/2 Heisenberg model on the triangular lattice with the antiferromagnetic first(J1 ) and second-neighbor (J2 ) interactions by means of density matrix renormalization group
(DMRG). Beside the three sublattice ordered Neel phase and a stripe antiferromagnetic phase
at smaller (~0.07) and larger J2 (~0.16) sides, we find a quantum spin liquid in the intermediate
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range of the J2. We show that there are two topological sectors. The odd sector (by pinning
spinons at cylinder boundaries) is very robust, while the even topological sector has higher
energy for smaller systems possibly due to a competing chiral state. We demonstrate the
stabilization of the possible Z2 spin liquid in both sectors with the increase of the system width.
We analyze the quantum numbers of different near degenerating states, and discuss the possible
characterization of the Z2 spin liquid.
Dale J. Van Harlingen
Transport and Josephson phenomena in hybrid superconductor-topological insulator
devices
We are studying the transport properties of hybrid S-TI-S nanoscale devices fabricated by
depositing superconductor electrodes onto the surface of topological insulators. In top-gated
Nb-Bi2Se3-Nb junctions, we have measured the Josephson supercurrent and conductance as
a function of geometry, temperature, and gate voltage in order to determine the nature of the
electronic transport. The supercurrent exhibits a sharp drop as a function of gate doping that
may be explained by the relocation of the topological surface state from above to below trivial
conducting surface states formed by band-banding near the surface. We find that the magnetic
field modulation of the supercurrent in Josephson junctions and dc SQUIDs exhibits anomalous
features that are consistent with a 4 -periodic sin( /2)-component in the junction currentphase relation. We consider whether this could arise from the nucleation of Majorana bound
states in the junction and explore schemes for manipulating and ultimately braiding these exotic
excitations.
Ashvin Vishwanath
University of California at Berkeley
Topology and quantum coherence in `hot’ matter
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Password: Symmetries
Please see workshop staff for a secure Wi-Fi connection username and password at Keller Hall
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WORKSHOP PARTICIPANT LIST
David Aasen
- IQIM
david@aasen.ca
Alexander Abanov
Department of Physics &
Astronomy
alexandre.abanov@stonybrook.
edu
Jan Borchmann
McGill University
jan.borchmann@mail.mcgill.ca
Terence Bretz-Sullivan
bretz038@umn.edu
Barry Bradlyn
Yale University
barry.bradlyn@yale.edu
Jason Alicea
aliceaj@caltech.edu
Fiona Burnell
fburnell@umn.edu
Alexander Altland
Institute for theoretical physics
alexal@thp.uni-koeln.de
Vladimir Bychkov
bychk001@umn.edu
James Analytis
University of California,
Berkeley
analytis@berkeley.edu
Jiashen Cai
caixx266@umn.edu
Yilikal Ayino
ayino@physics.umn.edu
Tankut Can
Simons Center for Geometry and
Physics
tcan@scgp.stonybrook.edu
Dmitry Bagrets
Institute for Theoretical Physics,
dmitry.bagrets@uni-koeln.de
Pak On Chan
University of Illinois at UrbanaChampaign
atma.pochan@gmail.com
Leon Balents
Kavli Institute for Theoretical
Physics
balents@kitp.ucsb.edu
Xie Chen
xiechen@caltech.edu
Andrei Bernevig
bernevig@Princeton.edu
Tianran Chen
West Chester University
tchen@wcupa.edu
Morten Christensen
University of Minnesota and
The Niels Bohr Institute,
University of Copenhagen
mortenholmchristensen@gmail.
com
Tianbai Cui
cuixx105@umn.edu
Mahendra DC
madc0002@umn.edu
Lingjie Du
Rice University
dulingjie@gmail.com
Rui-Rui Du
Rice University
rrd@rice.edu
Maxim Dzero
Kent State University
mdzero@kent.edu
Alex Edelman
aoe@uchicago.edu
Chun Chen
chen2698@umn.edu
Chen Fang
Massachusetts Institute of
Technology
fangc@mit.edu
Jun Chen
chenjuniop@gmail.com
Rafael Fernandes
rfernand@umn.edu
21
Lukasz Fidkowski
Stony Brook
lukasf@gmail.com
Tobias Gulden
FTPI, University of Minnesota
gulden@physics.umn.edu
Sergey Frolov
frolovsm@pitt.edu
Woods Halley
woods@woods1.spa.umn.edu
Han Fu
fuxxx254@umn.edu
M. Zahid Hasan
Princeton Univ., Physics Dept.
mzhasan@princeton.edu
Liang Fu
Technology
liangfu@mit.edu
Chris Heinrich
chrisheinrich@uchicago.edu
Sayed Ali Akbar Ghorashi
University of Houston
sghorashi@uh.edu
Alberto Hinojosa Alvarado
hinoj010@umn.edu
Charles Kane
Department of Physics and
Astronomy
kane@physics.upenn.edu
Jian Kang
jkang@umn.edu
Fulya Koc
kocxx002@umn.edu
Yevhen Kurianovych
kuria014@umn.edu
Michael Laskin
laskin@uchicago.edu
Leonid Glazman
Yale University
leonid.glazman@yale.edu
Chang-Tse Hsieh
kelvinsie@gmail.com
Allen Goldman
goldman@physics.umn.edu
Yichen Hu
huyichen@sas.upenn.edu
Alex Levchenko
Michigan State University
levchenko@pa.msu.edu
Roberto Grassi
rgrassi@umn.edu
Taylor Hughes
hughest@illinois.edu
Michael Levin
malevin@uchicago.edu
Gino Graziano
graziano@physics.umn.edu
Andrey Gromov
Stony Brook University
andrey.gromov@stonybrook.edu
Ilya Gruzberg
The Ohio State University
gruzberg.1@osu.edu
Thomas Iadecola
Boston University
iadecola@bu.edu
Yongjin Jiang
jiang975@umn.edu
Alex Kamenev
kamenev@physics.umn.edu
22
Chris Leighton
leighton@umn.edu
Mo Li
moli@umn.edu
Yangmu Li
yl@physics.umn.edu
Mengqun Li
mengqun@physics.umn.edu
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WORKSHOP PARTICIPANT LIST
Chien-Hung Lin
chlin@uchicago.edu
N. Phuan Ong
Princeton Univ
npo@princeton.edu
Konstantin Reich
kreich@umn.edu
Changjiang Liu
University of Minnesota cliu@physics.umn.edu
Peter Orth
peter.orth@kit.edu
Rosa Rodriguez Mota
McGill University
rosarm@physics.mcgill.ca
Joey Liu
liux1387@umn.edu
Ilana Percher
percher@physics.umn.edu
P.Paul Ruden
ruden@umn.edu
Geremia Massarelli
McGill University
geremia.massarelli@mail.mcgill.
ca
Tami Pereg-Barnea
McGill University
tamipb@physics.mcgill.ca
Shinsei Ryu
ryuu@illinois.edu
Ian Mondragon
University of Illinois, UrbanaChampaign
mondrag2@illinois.edu
Olexei Motrunich
California Institute of
Technology
motrunch@caltech.edu
Stevan Nadj-Perge
Delft University of Technology
(previously at Princeton
University)s.nadj-perge@
tudelft.nl
JJ Nelson
nelson@physics.umn.edu
Katja Nowack
Cornell University
katja.nowack@cornell.edu
Jesper Nygard
Niels Both Institute, University of
Copenhagen
nygard@nbi.dk
Brent Perreault
perre035@umn.edu
Dmitry Pikulin
University of British Columbia
pikulin@phas.ubc.ca
Frank Pollmann
Max Planck Institute for the
Physics of Complex Systems
frankp@pks.mpg.de
Michael Schuett
schuett@physics.umn.edu
Marc Schulz
mdschulz@umn.edu
Daniel Shaffer
shaff159@umn.edu
Vlad Pribiag
vpribiag@umn.edu
Donna Sheng
California State Univ. Northridge
donna.sheng@csun.edu
Yang Qi
Perimeter Institute for Theoretical
Physics
yangqi137@me.com
Qianhui Shi
qshi@physics.umn.edu
Armin Rahmani
UBC
rahmani@physics.ubc.ca
Ken Shiozaki
Department of Physics, Kyoto
University
shiozaki@scphys.kyoto-u.ac.jp
Gil Refael
refael@caltech.edu
Boris Shklovskii
Shklovsk@physics.umn.edu
23
Sujeet Shukla
Jorn W F Venderbos
California Institute of Technology Massachusetts Institute of
sshukla@caltech.edu
Technology
jwfv@mit.edu
Inti Sodemann Villadiego
Sagar Vijay
Technology
sodemann@mit.edu
Technology
sagarv@mit.edu
Justin Song
California Institute of Technology Ashvin Vishwanath
justin.song.cw@gmail.com
Berkeley
Nicolas Tarantino
ashvinv@berkeley.edu
nicolas.tarantino@stonybrook.edu Curt von Keyserlingk
Princeton Center for theoretical
Kunal Tiwari
Science
McGill University
curtvk@princeton.edu
tiwarik@physics.mcgill.ca
Yuxuan Wang
Alex Turzillo
University of WisconsinCalifornia Institute of Technology Madison
aturzillo@theory.caltech.edu
wang238@wisc.edu
Oriol Valls
otvalls@umn.edu
Dale Van Harlingen
dvh@illinois.edu
Daniel Varjas
Berkeley
dvarjas@berkeley.edu
Zitao Wang
California Institute of
Technology
zwang@caltech.edu
Xiaoyu Wang
xiaoyu@physics.umn.edu
Yuting Wang
wang4503@umn.edu
24
Chenjie Wang
cjwang@uchicago.edu
Ruiqi Xing
xingx090@umn.edu
Zedong Yang
yang4302@umn.edu
Xuzhe Ying
yingx052@umn.edu
Mengxing Ye
University of Michigan
ymuriel@umich.edu
Peng Yu
pey13@pitt.edu
Jiaming Zheng
zheng369@umn.edu
Michael Zudov
zudov@physics.umn.edu
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WORKSHOP DINNER
Centennial Showboat, Harriet Island West
100 Yacht club road, St Paul MN 55107
FROM THE UNIVERSITY OF MINNESOTA:
Take I-94 East to 5th St. exit, go straight. Follow 5th St. to Robert Street. Turn right
on Robert St. Take Robert to cross river to Fillmore Ave (stoplight after bridge). Turn
right onto Fillmore Ave and take a right onto Levee Road. Follow Levee Rd until it
ends at the Showboat parking lot.
Driving directions - http://www.riverrides.com/pages/misc/mapsb.html
25
INSTRUCTIONS FOR UPLOADING
TALKS TO THE WORKSHOP WEBSITE
Please submit a PDF (preferred format) of your talk slides by Friday, June 5, 2015 to be
included in the conference web archive. Please include your name in the file name.
1. Use the following link to access the folder: 2015_Symmetries&Interactions_workshop:
https://netfiles.umn.edu/xythoswfs/webview/_xy-17484837_1
2. Click on the “Upload” icon at the top right of the page
3. Select your file and click “Start Upload”
The folder page should populte with your file. Alternatively, the screen may display
this message: “The document was successfully uploaded to the folder, 2015_
Symmetries&Interactions_Workshop” It may also tell you that the directory is empty, but this
just means that you may not have permission to see the files.
All submitted talks will be archived online for general access at the University of Minnesota’s
Digital Conservancy. By submitting your talk slides you are agreeing to the Digital
Conservancy’s Copyright policy. For policy details see the website at: http://conservancy.umn.
edu
Please note that there will be a delay between your upload and final posting on the workshop
website. Once all talks have been submitted, participants will be notified by email. As always,
any questions may be addressed to ftpi-topological-workshop@physics.umn.edu.
***If you are having problems uploading your PDF please email it to the workshop email
address ftpi-topological-workshop@physics.umn.edu***
26
U
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STADIUM VILLAGE DINING GUIDE
27
ADDITIONAL LOCATIONS
1) William I. Fine Theoretical Physics Institute: 116 Church Street SE, 4th floor North building entrance
2) Workshop Location Friday PM - Sunday: Keller Hall 3-180, 200 Union Street SE
3) Workshop Location Friday AM and Workshop Hotel: The Commons Hotel, 615 Washington Ave SE
1)
2)
3)
M
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P
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28
POSTER SESSION
Quasi-one-dimensional Fibonacci Physics
David Aasen
California Institute of Technology - IQIM
Entanglement entropy of a disorder spin-orbit coupled superconductor
Jan Borchmann
McGill University
Splitting the topological ground-state degeneracy of parafermions in fractional quantum
Hall heterostructures
Chun Chen
Zero-bias peak in InSb nanowire
Jun Chen
Correlation effects in the capacitance of a gated carbon nanotube
Han Fu
Topological Crystalline Insulators Protected by one Glide Plane
Chen Fang
Framing anomaly in fractional quantum Hall states
Andrey Gromov
Exactly soluble model of disorder for FQH edge modes
Chris Heinrich
29
Diagnosing symmetry protected topological phases in crystalline topological insulators and
superconductors
Chang-Tse Hsieh
Universal symmetry-protected resonances in a spinful Luttinger liquid
Yichen Hu
Stroboscopic Symmetry-Protected Topological Phases
Thomas Iadecola
Boston University
Fractional Quantum Hall Effect in a Curved Space: Gravitational Anomaly and Electromagnetic
Response
Michael Laskin
Rashba induced space symmetry broken and scattering processes in graphene
Yue Liu
Disorder-induced phase transitions and delocalization in topological insulators
Ian Mondragon
University of Illinois, Urbana-Champaign
Dimensional crossover and cold-atom realization of topological Mott insulators
Peter Orth
Floquet topological insulators
Tami Pereg-Barnea
McGill University
30
p
O
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POSTER SESSION
Spectroscopy of Spin Liquid Dynamics
Brent Perreault
Crystal symmetry fractionalization and anomaly on the surface of topological crystalline
insulators
Yang Qi
Perimeter Institute for Theoretical Physics
Emergent supersymmetry from interacting Majoranas
Armin Rahmani
UBC
Impact of non-Abelian anyons on criticality
Marc Schulz
K-theory classification of topological crystalline insulators with space group symmetry
Ken Shiozaki
Department of Physics, Kyoto University
Stability of tensor network representation of string net states
Sujeet Shukla
Berry curvature induced nonlinear Hall effect in time-reversal invariant materials
Inti Sodemann Villadiego
31
Topological Currents in Gapped Dirac Systems
Justin Song
Effects of nonsymmorphic symmetries in crystalline topological insulators and superconductors
Daniel Varjas
Interaction-induced topological phases in strained TCI and graphene due to partially flat bands
Jorn W F Venderbos
A New Kind of Topological Quantum Order: Stationary Excitations and their Mobile
Composites
Sagar Vijay
Topological invariants for gauge theories and symmetry-protected topological phases
Chenjie Wang
Topological Surface States of Topological Crystalline Kondo Insulator SmB6
Mengxing Ye
University of Michigan
32
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Symmetries and Interactions in Topological Matter

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