Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session B55: Invited Session: Novel Topological Phases and Surface States in Strongly Interacting Systems |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Charles Kane, University of Pennsylvania Room: Four Seasons Ballroom 1 |
Monday, March 3, 2014 11:15AM - 11:51AM |
B55.00001: Highly entangled quantum states of matter Invited Speaker: Xiao-Gang Wen Highly entangled quantum matter is a new class of matter that correspond patterns of intricate quantum entanglement. The phases of matter have traditionally been classified by their symmetry properties described by group theory. For decades we believe that symmetry breaking states describe all possible phases of matter. However, the discovery of topological order suggested that Landau theory does not describe all quantum phases. In topological order, the phases are not described by the patterns of symmetry, but by the patterns of long-range quantum entanglement. Recently, we have identified a new class of states, called symmetry-protected topological order, which correspond to patterns of short-range quantum entanglement with symmetry. We find that this class of quantum phases and corresponding patterns of entanglement can be described by an abstract mathematical theory - group cohomology theory. In this talk, I will review the background and the basic theory of symmetry-protected topological phases. [Preview Abstract] |
Monday, March 3, 2014 11:51AM - 12:27PM |
B55.00002: Classification and Edge States of Symmetry Protected Topological Phases Invited Speaker: Xie Chen Symmetry protected topological (SPT) phases are gapped and nonfractionalized in the bulk but can have nontrivial edge states protected by the anomalous symmetry action on the boundary. In this talk, I discuss the classification of bosonic SPT phases using group cohomology and what their edge states are like in one, two and three dimensions. In 1D, edge states of SPT chains are degenerate and carry projective representations of the symmetry. In 2D SPT systems, the edge state is either symmetry breaking or gapless which can be protected by the chiral symmetry action on the 1D boundary. For 3D SPT states, a new possibility arises on the 2D boundary besides being symmetry breaking or gapless. The edge can be both gapped and symmetric and have fractional excitations. The fractional excitations transform under symmetry in a way that is not possible in 2D and hence reflect the nontrivial SPT order in the bulk. Explicit examples are given to illustrate the possibilities in different dimensions. [Preview Abstract] |
Monday, March 3, 2014 12:27PM - 1:03PM |
B55.00003: A symmetry-respecting topologically-ordered surface phase of 3d electron topological insulators Invited Speaker: Max Metlitski A 3d electron topological insulator (ETI) is a phase of matter protected by particle-number conservation and time-reversal symmetry. It was previously believed that the surface of an ETI must be gapless unless one of these symmetries is broken. A well-known symmetry-preserving, gapless surface termination of an ETI supports an odd number of Dirac cones. In this talk, I will show that in the presence of strong interactions, an ETI surface can actually be gapped and symmetry preserving, at the cost of carrying an intrinsic two-dimensional topological order. I will argue that such a topologically ordered phase can be obtained from the surface superconductor by proliferating the flux 2hc/e vortex. The resulting topological order consists of two sectors: a Moore-Read sector, which supports non-Abelian charge e/4 anyons, and an Abelian anti-semion sector, which is electrically neutral. The time-reversal and particle number symmetries are realized in this surface phase in an ``anomalous'' way: one which is impossible in a strictly 2d system. [Preview Abstract] |
Monday, March 3, 2014 1:03PM - 1:39PM |
B55.00004: Classification of interacting electronic topological insulators in three dimensions Invited Speaker: Chong Wang A fundamental open problem in condensed matter physics is how the dichotomy between conventional and topological band insulators is modified in the presence of strong electron interactions. We show that there are 6 new electronic topological insulators that have no non-interacting counterpart. Combined with the previously known band-insulators, these produce a total of 8 topologically distinct phases. Two of the new topological insulators have a simple physical description as Mott insulators in which the electron spins form spin analogs of the familiar topological band-insulator. The remaining are obtained as combinations of these two ``topological paramagnets'' and the topological band insulator. We prove that these 8 phases form a complete list of all possible interacting topological insulators, and are classified by a $Z_2^3$ group-structure. Experimental signatures are also discussed for these phases. [Preview Abstract] |
Monday, March 3, 2014 1:39PM - 2:15PM |
B55.00005: Stability of Topological Superconductors to Interactions and Surface Topological Order Invited Speaker: Lukasz Fidkowski Three-dimensional topological superconductors protected by time reversal symmetry are characterized by gapless Majorana cones on their surface. Free-fermion phases with this symmetry (class DIII) are indexed by an integer $Z$, of which $\nu=1$ is realized by the B phase of superfluid $^3 He$. Previously, it was believed that the surface must be gapless unless time-reversal symmetry is broken. In this talk, we argue that a fully symmetric and gapped surface is possible in the presence of strong interactions, if a special type of topological order appears on the surface. The topological order realizes time reversal symmetry in an anomalous way, one that is impossible to achieve in purely two dimensions. For odd $\nu$, the surface topological order must be non-Abelian, and propose the simplest non-Abelian topological order that contains electronlike excitations, $SO(3)_6$, with four quasiparticles, as a candidate surface state. We also discuss Abelian theories for the surface $\nu=2,4,8$; one particular consequence of our scheme is that $\nu=16$ admits a trivially gapped time reversal symmetric surface. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
1 Research Road, Ridge, NY 11961-2701
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700