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Topological response in gapless systems: from Weyl semimetals to metallic ferromagnets

Anton Burkov University of Waterloo

February 11, 2014

PIRSA:14020115
Specific heat and ac susceptibility measurements on the Spin Ice, Dy2Ti2O7

Jan Kycia University of Waterloo

February 11, 2014

PIRSA:14020114
13/14 PSI - Condensed Matter Review - Lecture 11

Alioscia Hamma University of Naples Federico II

February 11, 2014

PIRSA:14020049
Emergence of p+ip topological superconducting ground state in infinite-U Hubbard model on honeycomb lattice

Zheng-Cheng Gu Chinese University of Hong Kong

February 10, 2014

PIRSA:14020113
13/14 PSI - Cosmology Review - Lecture 9

Latham Boyle University of Edinburgh

February 10, 2014

PIRSA:14020017
Aharonov-Bohm effect in symmetry protected states

Luiz Santos Emory University

February 10, 2014

PIRSA:14020126
13/14 PSI - String Theory Review - Lecture 10

Davide Gaiotto Perimeter Institute for Theoretical Physics

February 10, 2014

PIRSA:14020028
Topological phases in graphene

Zlatko Papic University of Leeds

February 10, 2014

PIRSA:14020134
13/14 PSI - Condensed Matter Review - Lecture 10

Alioscia Hamma University of Naples Federico II

February 10, 2014

PIRSA:14020046
Introduction to Effective Field Theories - Lecture 10

Cliff Burgess McMaster University

February 07, 2014

PIRSA:14020092
13/14 PSI - Cosmology Review - Lecture 8

Latham Boyle University of Edinburgh

February 07, 2014

PIRSA:14020014
13/14 PSI - String Theory Review - Lecture 9

Davide Gaiotto Perimeter Institute for Theoretical Physics

February 07, 2014

PIRSA:14020027

Topological response in gapless systems: from Weyl semimetals to metallic ferromagnets

Anton Burkov University of Waterloo

February 11, 2014

PIRSA:14020115

Standard picture of a topologically-nontrivial phase of matter is an insulator with a bulk energy gap, but metallic surface states, protected by the bulk gap. Recent work has shown, however, that certain gapless systems may also be topologically nontrivial, in a precise and experimentally observable way. In this talk I will review our work on a class of such systems, in which the nontrivial topological properties arise from the existence of nondegenerate point band-touching nodes (Weyl nodes) in their electronic structure. Weyl nodes generally exist in any three-dimensional material with a broken time-reversal or inversion symmetry. Their effect is particularly striking, however, when the nodes coincide with the Fermi energy and no other states at the Fermi energy exist. Such "Weyl semimetals" have vanishing bulk density of states, but have gapless metallic surface states with an open (unlike in a regular two-dimensional metal) Fermi surface ("Fermi arc"). I will discuss our proposal to realize Weyl semimetal state in a heterostructure, consisting of alternating layers of topological and ordinary insulator, doped with magnetic impurities. I will further show that, apart from Weyl semimetals, even such "ordinary" materials as common metallic ferromagnets, in fact also possess Weyl nodes in the electronic structure, leading to the appearance of chiral Fermi-arc surface states and the corresponding contribution to their intrinsic anomalous Hall conductivity.
Specific heat and ac susceptibility measurements on the Spin Ice, Dy2Ti2O7

Jan Kycia University of Waterloo

February 11, 2014

PIRSA:14020114

Some time ago (1999), Dy2Ti2O7, was shown to be a magnetic analog of water ice, and thus dubbed "spin ice". Recently, theories and experiments have developed the perspective of viewing excitations within the low temperature phase of this spin ice as monopoles. I will present early results of specific heat, ac susceptibility and magnetization measurements as well as my group's recent results on this system
13/14 PSI - Condensed Matter Review - Lecture 11

Alioscia Hamma University of Naples Federico II

February 11, 2014

PIRSA:14020049
Emergence of p+ip topological superconducting ground state in infinite-U Hubbard model on honeycomb lattice

Zheng-Cheng Gu Chinese University of Hong Kong

February 10, 2014

PIRSA:14020113

In this talk, I will show the emergence of p+ip topological superconducting ground state in infinite-U Hubbard model on honeycomb lattice, from both state-of-art Grassmann tensor-network numerical approach and quantum field theory approach.
13/14 PSI - Cosmology Review - Lecture 9

Latham Boyle University of Edinburgh

February 10, 2014

PIRSA:14020017
Aharonov-Bohm effect in symmetry protected states

Luiz Santos Emory University

February 10, 2014

PIRSA:14020126

Symmetry protected topological (SPT) states are generalizations of topological band insulators to interacting systems. They possess a gapped bulk spectrum together with symmetry protected edge states, with no topological order. There has been recently an intense effort to classify SPT states both in terms of group cohomology as well as from the point of view of effective field theories. An interesting related question is to understand the structute of lattice models that realize SPT physics. In this talk, I shall present a class of lattice models describing the egde of non-chiral two-dimensional bosonic SPT states protected by Z_N symmetry. A crucial aspect of the construction relies on finding the correct non-trivial Z_N symmetry realizations on the edge consistent with all the possible classes of SPT states. Then I shall discuss the Aharonov-Bohm effect on the many-body SPT state by studying this many-body effect on the aforementioned gapless edge states. The effect of a Z_N gauge flux on the egde states is formulated in terms of twisted boundary conditions of the lattice models. The low energy spectral shifts due to the gauge flux are shown to depend on each of the SPT classes in a predictable way. I shall, in the course of this talk, present numerical results of exact diagonalization of our lattice Hamiltonians that support this analysis. This work is done in collaboration with Juven Wang and
appears in arXiv:1310.8291.
13/14 PSI - String Theory Review - Lecture 10

Davide Gaiotto Perimeter Institute for Theoretical Physics

February 10, 2014

PIRSA:14020028
Topological phases in graphene

Zlatko Papic University of Leeds

February 10, 2014

PIRSA:14020134

As realized for the first time in 1980s, quantum many-body systems in reduced spatial dimensions can sometimes undergo a special type of ordering which does not break any symmetry but introduces long-range entanglement and emergent excitations that have radically different properties from their original constituents. Most of our experimental knowledge of such ``topological" phases of matter comes from studies of two-dimensional electron gases in GaAs semiconductors in high magnetic fields and at low temperatures. In the first part of this talk, I will give an introduction to these systems and review some latest theoretical developments related to their entanglement properties. In the second part, I will discuss new possibilities
for experimental realizations of topological phases in bilayer graphene. I will present evidence that this material supports an ``even-denominator" fractional state, related to the Moore-Read state, whose observation has recently been reported. Finally, I will outline several proposals based on the tunability of the electron-electron interactions in bilayer graphene which might enable further experimental progress beyond GaAs.
13/14 PSI - Condensed Matter Review - Lecture 10

Alioscia Hamma University of Naples Federico II

February 10, 2014

PIRSA:14020046
Introduction to Effective Field Theories - Lecture 10

Cliff Burgess McMaster University

February 07, 2014

PIRSA:14020092
13/14 PSI - Cosmology Review - Lecture 8

Latham Boyle University of Edinburgh

February 07, 2014

PIRSA:14020014
13/14 PSI - String Theory Review - Lecture 9

Davide Gaiotto Perimeter Institute for Theoretical Physics

February 07, 2014

PIRSA:14020027

Title	Date	Collection	Type	Info
Topological response in gapless systems: from Weyl semimetals to metallic ferromagnets	2014‑02‑11	Emergence in Complex Systems	Conference	View details
Specific heat and ac susceptibility measurements on the Spin Ice, Dy2Ti2O7	2014‑02‑11	Emergence in Complex Systems	Conference	View details
13/14 PSI - Condensed Matter Review - Lecture 11	2014‑02‑11	13/14 PSI - Condensed Matter Review	Course	View details
Emergence of p+ip topological superconducting ground state in infinite-U Hubbard model on honeycomb lattice	2014‑02‑10	Emergence in Complex Systems	Conference	View details
13/14 PSI - Cosmology Review - Lecture 9	2014‑02‑10	13/14 PSI - Cosmology Review	Course	View details
Aharonov-Bohm effect in symmetry protected states	2014‑02‑10	Emergence in Complex Systems	Conference	View details
13/14 PSI - String Theory Review - Lecture 10	2014‑02‑10	13/14 PSI - String Theory Review	Course	View details
Topological phases in graphene	2014‑02‑10	Emergence in Complex Systems	Conference	View details
13/14 PSI - Condensed Matter Review - Lecture 10	2014‑02‑10	13/14 PSI - Condensed Matter Review	Course	View details
Introduction to Effective Field Theories - Lecture 10	2014‑02‑07	Introduction to Effective Field Theories	Course	View details
13/14 PSI - Cosmology Review - Lecture 8	2014‑02‑07	13/14 PSI - Cosmology Review	Course	View details
13/14 PSI - String Theory Review - Lecture 9	2014‑02‑07	13/14 PSI - String Theory Review	Course	View details

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