Condensed Matter

Displaying 985 - 996 of 1218

Symmetry Enriched Quantum Spin Ices On the Pyrochlore Lattice

Gang Chen Fudan University
December 06, 2013

PIRSA:13120055
Condensed Matter
The Amplitude Mode in Condensed Matter : Higgs Hunting on a Budget

Daniel Arovas University of California, San Diego
November 19, 2013

PIRSA:13110054
Condensed Matter
Topological States in Strongly-Correlated Materials

Kai Sun University of Michigan–Ann Arbor
November 15, 2013

PIRSA:13110082
Condensed Matter
Z2 spin liquid in kagome Heisenberg antiferromagnet

Yuan Wan Chinese Academy of Sciences
November 05, 2013

PIRSA:13110086
Condensed Matter
Silicene - a Wonder Electron Carpet

Baskaran Ganapathy Institute of Mathematical Sciences
October 29, 2013

PIRSA:13100128
Condensed Matter
Wilsonian and large N approaches to non-Fermi liquids

Shamit Kachru Stanford University
October 22, 2013

PIRSA:13100109
Condensed Matter
Geometry of quantum phases and emergent Newtonian dynamics

Anatoli Polkovnikov Boston College
October 15, 2013

PIRSA:13100083
Condensed Matter
Fractional solitons on the edge of the Fractional Quantum Hall states

Paul Wiegmann University of Chicago - James Franck Institute
October 10, 2013

PIRSA:13100073
Condensed Matter
From Supersolidity to Giant Plasticity: Defects in Quantum Crystals

John Beamish University of Alberta
October 09, 2013

PIRSA:13100065
Condensed Matter
Geometry and Topology in the Fractional Quantum Hall Effect

Duncan Haldane Princeton University
October 07, 2013

PIRSA:13100086
Condensed Matter
Self-organized topological state with Majorana fermions

Marcel Franz University of British Columbia
September 17, 2013

PIRSA:13090071
Condensed Matter
Edge states at domain wall junctions in supersymmetric gauge theory

Davide Gaiotto Perimeter Institute for Theoretical Physics
September 13, 2013

PIRSA:13090074
Condensed Matter

Symmetry Enriched Quantum Spin Ices On the Pyrochlore Lattice

Gang Chen Fudan University
December 06, 2013

PIRSA:13120055
Condensed Matter
Quantum spin liquid (QSL) is an exotic phase of matter and provides an interesting example of emergent non-locality. Even though many materials have been proposed as candidates for QSLs, there is no direct confirmation of QSLs in any of these systems. Quantum spin ice (QSI) is a physical realization of U(1) QSLs on the pyrochlore lattice. We consider a class of electron systems in which dipolar-octupolar Kramers doublets arise on the pyrochlore lattice. In the localized limit, the Kramers doublets are described by the effective spin 1/2 pseudospins. The most general nearest-neighbor exchange model between these pseudospins is the XYZ model. We show that this XYZ model exhibit two distinct symmetry enriched QSI phases, that we dub dipolar QSI and octupolar QSI. This XYZ model is absent from the notorious sign problem for a quantum Monte Carlo simmulation. We also discuss the potential relevance to real material systems.
The Amplitude Mode in Condensed Matter : Higgs Hunting on a Budget

Daniel Arovas University of California, San Diego
November 19, 2013

PIRSA:13110054
Condensed Matter
The amplitude mode is a ubiquitous phenomenon in systems with broken continuous symmetry and effective relativistic dynamics, and has been observed in magnets, charge density waves, cold atom systems, and superconductors. It is a simple analog of the Higgs boson of particle physics. I will discuss the properties of the amplitude mode and its somewhat surprising visibility in two-dimensional systems, recently confirmed in cold atom experiments. The behavior in the vicinity of a quantum critical point will be stressed, comparing theoretical, numerical, and experimental results.
Topological States in Strongly-Correlated Materials

Kai Sun University of Michigan–Ann Arbor
November 15, 2013

PIRSA:13110082
Condensed Matter
In the study of strongly-correlated insulators, a long-standing puzzle remained open for over 40 years. Some Kondo insulators (or mixed-valent insulators) display strange electrical transport that cannot be understood if one assumes that it is governed by the three-dimensional bulk. In this talk, I show that some 3D Kondo insulators have the right ingredients to be topological insulators, which we called “topological Kondo insulators”. For a topological Kondo insulator, the low-temperature transport is dominated by the 2D surface rather than the 3D bulk, because the bulk of this material is an insulator while its surface is a topologically-protected 2D metal. This theoretical picture offers a natural explanation for the long-standing puzzle mentioned above. In addition, we also find that Kondo insulators can support another type of nontrivial topological structure protected by lattice symmetries, which we called “topological crystalline Kondo insulators”. In particular, we predict that SmB$_6$ is both a topological Kondo insulator and a topological crystalline Kondo insulator and I will also discuss recent experiments, which reveal the surface states in SmB$_6$.
Z2 spin liquid in kagome Heisenberg antiferromagnet

Yuan Wan Chinese Academy of Sciences
November 05, 2013

PIRSA:13110086
Condensed Matter
A quantum spin liquid is a hypothesized ground state of a magnet without long-range magnetic order. Similar to a liquid, which is spatially uniform and strongly correlated, a quantum spin liquid preserves all the symmetries and exhibits strong correlations between spins. First proposed by P. W. Anderson in 1973, it has remained a conjecture until recently. In the past couple of years, numerical studies have provided strong evidences for quantum spin liquid in a simple model, the kagome Heisenberg antiferromagnet. In this talk, I will describe a low-energy effective theory for this magnet in terms of a lattice gauge theory with the simplest possible mathematical structure (a group of two elements, namely Z2). I will show that the theory reproduces many characteristic features observed numerically, thereby providing a bridge between the numeircs and the analytics. Furthermore, I will present theoretical predictions which could be tested in future numerical studies.
Silicene - a Wonder Electron Carpet

Baskaran Ganapathy Institute of Mathematical Sciences
October 29, 2013

PIRSA:13100128
Condensed Matter
Graphene is a 2 dimensional net of strongly bonded carbon atoms. This magic carpet has taken us to new heights in the last decade. Silicene and Germanene are analogue nets, made of silicon and germanium atoms respectively, but with a relatively weaker chemical bond. I will argue that these carpets perform some new tricks by not being a carbon copy of graphene. We have suggested [1] that silicene and germanene are Mott insulators and potential abode for room temperature superconductivity, quantum spin liquids and more
Wilsonian and large N approaches to non-Fermi liquids

Shamit Kachru Stanford University
October 22, 2013

PIRSA:13100109
Condensed Matter
We use Wilsonian RG and large N techniques to study the quantum field theory of a critical boson interacting with a Fermi surface, and compare/contrast the results with those coming from holography.
Geometry of quantum phases and emergent Newtonian dynamics

Anatoli Polkovnikov Boston College
October 15, 2013

PIRSA:13100083
Condensed Matter
In the first part of this talk I will discuss how one can characterize geometry of quantum phases and phase transitions based on the Fubini-Study metric, which characterizes the distance between ground state wave-functions in the external parameter space. This metric is closely related to the Berry curvature. I will show that there are new geometric invariants based on the Euler characteristic. I will also show how one can directly measure this metric tensor in simple dynamical experiments. In the second part of the talk I will discuss emergent nature of macroscopic equations of motion (like Newton's equations) showing that they appear in the leading order of non-adiabatic expansion. I will show that the Berry curvature gives the Coriolis force and the Fubini-Study metric tensor is closely related to the inertia mass. Thus I will argue that any motion (not necessarily motion in space) is geometrical in nature.
Fractional solitons on the edge of the Fractional Quantum Hall states

Paul Wiegmann University of Chicago - James Franck Institute
October 10, 2013

PIRSA:13100073
Condensed Matter
We argue that dynamics of gapless Fractional Quantum Hall Edge states is essentially non-linear and that it features fractionally quantized solitons propagating along the edge. Observation of solitons would be a direct evidence of fractional charges. We show that the non-linear dynamics of the Laughlin's FQH state is governed by the quantum Benjamin-Ono equation.
From Supersolidity to Giant Plasticity: Defects in Quantum Crystals

John Beamish University of Alberta
October 09, 2013

PIRSA:13100065
Condensed Matter
In 2004, Kim and Chan reported torsional oscillator experiments on 4He crystals which showed evidence of “non-classical rotational inertia”, the mass decoupling expected for a long-sought “supersolid” state. It soon became clear that this behavior is not a property of perfect crystals – defects are involved. In 2007, we made elastic measurements which showed, to our surprise, that the shear modulus of solid 4He increases dramatically below 0.2 K, with the same dependence on temperature, amplitude and 3He impurity concentration as the torsional oscillator anomaly. These shear modulus changes are due to dislocations and their interactions with impurities and vacancies. Our experiments raised an obvious question – could the torsional oscillator behavior be an artifact of the elastic changes, rather than evidence of supersolidity? During the past two years it has become clear that the answer is “yes” and interest has focused on the properties of dislocations in a quantum solid like 4He. By growing high quality single crystals in optical cells, we have now been able to explore the behavior of dislocations in 4He in unprecedented detail. In some crystals the dislocations reduce the shear modulus by more than 80%, an extraordinary effect we describe as “giant plasticity”. Solid helium has proved to be an ideal system in which to do materials science, as well as to address fundamental questions about quantum solids.
Geometry and Topology in the Fractional Quantum Hall Effect

Duncan Haldane Princeton University
October 07, 2013

PIRSA:13100086
Condensed Matter
The FQHE is exhibited by electrons moving on a 2D surface through which a magnetic flux passes, giving rise to flat bands with extensive degeneracy (Landau levels). The degeneracy of a partially-filled Landau level is lifted by Coulomb repulsion between the electrons, which at certain rational fillings, leads to gapped incompressible topologically-ordered fluid states exhibiting the FQHE. Successful model wavefunctions for FQHE states, such as the Laughlin and Moore-Read states, are surprisingly related to Euclidean conformal field theory, even though they are gapped incompressiible quantum fluids with a fundamental unit of area set by the area per magnetic flux quantum h/e. The model wavefunctions are parametrized by a continuously-variable Euclidean metric, just like the Euclidean conformal group of the cft to which they are related. This metric is fixed locally both by the form of the projected Coulomb interaction within the partially-filled Landau level, and by local gradients of the tangential electric field on the 2D surface, promoting it from a static flat metric fixed globally by the cft, to a dynamic local physical degree of freedom of the FQHE fluid with area-preserving zero-point fluctuations that leave an imprint in the ground-state structure function. The curious connection to cft appears to be that the Virasoro algebra plays a fundament role in both cft and FQHE, for apparently-unrelated reasons. In the FQHE it derives from a chiral "gravitional" (geometric) topologically-protected anomaly at the edge of the fluid that is also revealed in the entanglement spectrum of a cut through the bulk fluid.
Self-organized topological state with Majorana fermions

Marcel Franz University of British Columbia
September 17, 2013

PIRSA:13090071
Condensed Matter
Topological phases, quite generally, are difficult to come by. They either occur under rather extreme conditions (e.g. the quantum Hall liquids, which require high sample purity, strong magnetic fields and low temperatures) or demand fine tuning of system parameters, as in the majority of known topological insulators. Many perfectly sensible topological phases, such as the Weyl semimetals and topological superconductors, remain experimentally undiscovered. In this talk I will introduce a system in which a key dynamical parameter adjusts itself in response to the changing external conditions so that the ground state naturally favors the topological phase. The system consists of a quantum wire formed of individual magnetic atoms placed on the surface of an ordinary s-wave superconductor. It realizes the Kitaev paradigm of topological superconductivity when the wavevector characterizing the emergent spin helix dynamically self-tunes to support the topological phase.
Edge states at domain wall junctions in supersymmetric gauge theory

Davide Gaiotto Perimeter Institute for Theoretical Physics
September 13, 2013

PIRSA:13090074
Condensed Matter

Title	Speaker(s)	Date	Talk Type	Info link
Symmetry Enriched Quantum Spin Ices On the Pyrochlore Lattice	Gang Chen	2013-12-06	Scientific Series	View details
The Amplitude Mode in Condensed Matter : Higgs Hunting on a Budget	Daniel Arovas	2013-11-19	Scientific Series	View details
Topological States in Strongly-Correlated Materials	Kai Sun	2013-11-15	Scientific Series	View details
Z2 spin liquid in kagome Heisenberg antiferromagnet	Yuan Wan	2013-11-05	Scientific Series	View details
Silicene - a Wonder Electron Carpet	Baskaran Ganapathy	2013-10-29	Scientific Series	View details
Wilsonian and large N approaches to non-Fermi liquids	Shamit Kachru	2013-10-22	Scientific Series	View details
Geometry of quantum phases and emergent Newtonian dynamics	Anatoli Polkovnikov	2013-10-15	Scientific Series	View details
Fractional solitons on the edge of the Fractional Quantum Hall states	Paul Wiegmann	2013-10-10	Scientific Series	View details
From Supersolidity to Giant Plasticity: Defects in Quantum Crystals	John Beamish	2013-10-09	Scientific Series	View details
Geometry and Topology in the Fractional Quantum Hall Effect	Duncan Haldane	2013-10-07	Scientific Series	View details
Self-organized topological state with Majorana fermions	Marcel Franz	2013-09-17	Scientific Series	View details
Edge states at domain wall junctions in supersymmetric gauge theory	Davide Gaiotto	2013-09-13	Scientific Series	View details

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Symmetry Enriched Quantum Spin Ices On the Pyrochlore Lattice

The Amplitude Mode in Condensed Matter : Higgs Hunting on a Budget

Topological States in Strongly-Correlated Materials

Z2 spin liquid in kagome Heisenberg antiferromagnet

Silicene - a Wonder Electron Carpet

Wilsonian and large N approaches to non-Fermi liquids

Geometry of quantum phases and emergent Newtonian dynamics

Fractional solitons on the edge of the Fractional Quantum Hall states

From Supersolidity to Giant Plasticity: Defects in Quantum Crystals

Geometry and Topology in the Fractional Quantum Hall Effect

Self-organized topological state with Majorana fermions

Edge states at domain wall junctions in supersymmetric gauge theory

Symmetry Enriched Quantum Spin Ices On the Pyrochlore Lattice

The Amplitude Mode in Condensed Matter : Higgs Hunting on a Budget

Topological States in Strongly-Correlated Materials

Z2 spin liquid in kagome Heisenberg antiferromagnet

Silicene - a Wonder Electron Carpet

Wilsonian and large N approaches to non-Fermi liquids

Geometry of quantum phases and emergent Newtonian dynamics

Fractional solitons on the edge of the Fractional Quantum Hall states

From Supersolidity to Giant Plasticity: Defects in Quantum Crystals

Geometry and Topology in the Fractional Quantum Hall Effect

Self-organized topological state with Majorana fermions

Edge states at domain wall junctions in supersymmetric gauge theory