Talks

12877 - 12888 of 19958 Results

Amplitude mode of the d-density wave state and its relevance to high-Tc cuprates

Ipsita Mandal Shiv Nadar University

November 30, 2012

PIRSA:12110089

Condensed Matter
Statistical Mechanics - Lecture 15

John Berlinsky McMaster University

November 30, 2012

PIRSA:12110037
Beyond the Search for Majorana

Yi-Zhuang You University of California, San Diego

November 30, 2012

PIRSA:12110088

Condensed Matter
Quantum Field Theory 2 - Lecture 15

Francois David CEA Saclay

November 30, 2012

PIRSA:12110018

High Energy Physics
Universal driven dynamics near phase transitions : Kibble-Zurek ramps with and without an order parameter

Anushya Chandran Perimeter Institute for Theoretical Physics

November 29, 2012

PIRSA:12110095

Condensed Matter
Fractional quantum Hall effect and tunable interactions

Zlatko Papic University of Leeds

November 29, 2012

PIRSA:12110081

Condensed Matter
Fractional Chern Insulators

Titus Neupert ETH Zurich

November 29, 2012

PIRSA:12110080

Condensed Matter
Statistical Mechanics - Lecture 14

John Berlinsky McMaster University

November 29, 2012

PIRSA:12110036
Quantum Field Theory 2 - Lecture 14

Francois David CEA Saclay

November 29, 2012

PIRSA:12110017

High Energy Physics
Dyon condensation in topological Mott insulators

Gil Young Cho Pohang University of Science and Technology

November 28, 2012

PIRSA:12110087

Condensed Matter
Wiring up Quantum Systems: Fun with Artificial Atoms and Microwave Photons

Steve Girvin Yale University

November 28, 2012

PIRSA:12110041

Condensed Matter
12/13 PSI Researcher Presentation

Steve Girvin Yale University

November 28, 2012

PIRSA:12110093

Condensed Matter

Amplitude mode of the d-density wave state and its relevance to high-Tc cuprates

Ipsita Mandal Shiv Nadar University

November 30, 2012

PIRSA:12110089

Condensed Matter

We study the spectrum of the amplitude mode, the analog of the Higgs mode in high energy physics, for the d-density wave (DDW) state proposed to describe the anomalous phenomenology of the pseudogap phase of the high Tc cuprates. Even though the state breaks translational symmetry by a lattice spacing and is described by a particle-hole singlet order parameter at the wave vector q = Q = (pi, pi), remarkably, we find that the amplitude mode spectrum can have peaks at both q = (0, 0) and q = Q = (pi , pi). In general, the spectra is non-universal, and, depending on the microscopic parameters, can have one or two peaks in the Brillouin zone, signifying confluence of two kinds of magnetic excitations. In light of the recent unexpected observations of multiple magnetic excitations in the pseudogap phase our theory sheds important light on how multiple inelastic neutron peaks at different wave vectors can arise even with an order parameter that condenses at Q = (pi, pi). [Reference: arXiv:1207.6834]
Statistical Mechanics - Lecture 15

John Berlinsky McMaster University

November 30, 2012

PIRSA:12110037
Beyond the Search for Majorana

Yi-Zhuang You University of California, San Diego

November 30, 2012

PIRSA:12110088

Condensed Matter

The search for Majorana zero-modes in condensed matter system has attract increasing research interests recently. Looking for Majorna zero-mode is actually looking for topologically protected ground state degeneracy. The topological degeneracies on closed manifolds have been used to discover/define topological order in many-body systems, which contain excitations with fractional statistics. In this talk, I will present our recent work on new types of topological degeneracy induced by condensing anyons along a line in 2D topological ordered states. Such topological degeneracy can be viewed as carried by each end of the line-defect, which is a generalization of Majorana zero-modes. The ends of line-defects carry projective non-Abelian statistics even though they are produced by condensation of Abelian anyons, and braiding them allow us to perform fault tolerant quantum computations.
Quantum Field Theory 2 - Lecture 15

Francois David CEA Saclay

November 30, 2012

PIRSA:12110018

High Energy Physics
Universal driven dynamics near phase transitions : Kibble-Zurek ramps with and without an order parameter

Anushya Chandran Perimeter Institute for Theoretical Physics

November 29, 2012

PIRSA:12110095

Condensed Matter

Near a critical point, the equilibrium relaxation time of a system diverges and any change of control parameters leads to non-equilibrium behavior. The Kibble-Zurek (KZ) problem is to determine
the evolution of the system when the change is slow. In this talk, I will introduce a non-equilibrium scaling limit in which these evolutions are universal and define a KZ universality classification with exponents and scaling functions. I will illustrate the physics accessible in this
scaling limit in simple classical and quantum model theories with symmetry-breaking transitions.

I will then turn to the KZ problem near quantum phase transitions without a local order parameter.
First, I will introduce the necessary background through the example of the Ising gauge theory/generalized toric code. Using duality and the scaling theory developed in the first part of the talk, I will then argue that the late time dynamics exhibits a slow coarsening of the string-net
that is condensed in the starting topologically ordered state. I will also discuss a time dependent amplification of the energy splitting between topologically degenerate states on closed manifolds and the dangerous irrelevance of gapped modes. Finally, I will extend these ideas to the non-abelian SU(2)_k ordered phases of the relevant Levin-Wen models.
Fractional quantum Hall effect and tunable interactions

Zlatko Papic University of Leeds

November 29, 2012

PIRSA:12110081

Condensed Matter

In this talk I will review some existing experimental methods, as well as a few recent theoretical proposals, to tune the interactions in a number of low-dimensional systems exhibiting the fractional quantum Hall effect (FQHE). The materials in question include GaAs wide quantum wells and multilayer graphene, where the tunability of the electron-electron interactions can be achieved via modifying the band structure, dielectric environment of the sample, by tilting the magnetic field or varying the mass tensor, and by mixing of electronic subbands and Landau levels. Because the interesting topological (and in particular, non-Abelian) states arise solely due to strong interactions, the ability to tune them is essential for ``designing" more robust FQHE states. Furthermore, I will argue that some of these mechanisms can also be used to probe the subtle aspects of FQHE physics, such as the breaking of particle-hole symmetry between the Moore-Read Pfaffian and anti-Pfaffian states, and the transition between FQHE fluids and broken-symmetry states due to the fluctuation of the intrinsic geometric degree of freedom.
Fractional Chern Insulators

Titus Neupert ETH Zurich

November 29, 2012

PIRSA:12110080

Condensed Matter

Fractional Chern insulators (FCIs) are topologically ordered states of interacting fermions that share their universal properties with fractional quantum Hall states in Landau levels. FCIs have been found numerically in a variety of two-dimensional lattice models upon partially filling an almost dispersionless band with nontrivial topological character with repulsively interacting fermions. I will show how FCIs emerge in bands with Chern number C=1 and C=2 and in Z_2 topological insulators, where the latter are accompanied by a spontaneous breaking of time-reversal symmetry. Further, I will discuss the relevance of the noncommutative quantum geometry of the flat topological band to the stability of FCIs and how they can be distinguished from phases of spontaneously broken point group symmetry, such as charge density waves.
Statistical Mechanics - Lecture 14

John Berlinsky McMaster University

November 29, 2012

PIRSA:12110036
Quantum Field Theory 2 - Lecture 14

Francois David CEA Saclay

November 29, 2012

PIRSA:12110017

High Energy Physics
Dyon condensation in topological Mott insulators

Gil Young Cho Pohang University of Science and Technology

November 28, 2012

PIRSA:12110087

Condensed Matter

We consider quantum phase transitions out of topological Mott insulators in which the ground state of the fractionalized excitations (fermionic spinons) is topologically non-trivial. The spinons in topological Mott insulators are coupled to an emergent compact U(1) gauge field with a so-called "axion" term. We study the confinement transitions from the topological Mott insulator to broken symmetry phases, which may occur via the condensation of dyons. Dyons carry both "electric" and "magnetic" charges, and arise naturally in this system because the monopoles of the emergent U(1) gauge theory acquires gauge charge due to the axion term. It is shown that the dyon condensate, in general, induces simultaneous current and bond orders. When the magnetic transition is driven by dyon condensation, we identify the bond order as valence bond solid order and the current order as scalar spin chirality order. Hence, the confined phase of the topological Mott insulator is an exotic phase where the scalar spin chirality and the valence bond order coexist and appear via a single transition. If time allows, I will also discuss our recent work on the proximate symmetry-broken phases of Z2 spin liquid on Kagome lattice.
Wiring up Quantum Systems: Fun with Artificial Atoms and Microwave Photons

Steve Girvin Yale University

November 28, 2012

PIRSA:12110041

Condensed Matter

A revolution is underway in the construction of ‘artificial atoms’ out of superconducting electrical circuits. These macroscopic ‘atoms’ have quantized energy levels and can emit and absorb quanta of light (in this case microwave photons), just like ordinary atoms. Unlike ‘real’ atoms, the properties of these artificial atoms can be engineered to suit various particular applications, and they can be connected together by wires to form quantum ‘computer chips.’ This so-called ‘circuit QED’ architecture has given us the ability to do non-linear quantum optics in electrical circuits at the single photon level. It is now possible to entangle multiple qubits, count individual microwave photons, create large ‘Schrödinger cat’ photon states and perform quantum feedback. This talk will present an elementary introduction to the field.
12/13 PSI Researcher Presentation

Steve Girvin Yale University

November 28, 2012

PIRSA:12110093

Condensed Matter

Title	Date	Collection	Type	Info
Amplitude mode of the d-density wave state and its relevance to high-Tc cuprates	2012‑11‑30	Quantum Matter	Scientific Series	View details
Statistical Mechanics - Lecture 15	2012‑11‑30	12/13 PSI - Statistical Mechanics	Course	View details
Beyond the Search for Majorana	2012‑11‑30	Quantum Matter	Scientific Series	View details
Quantum Field Theory 2 - Lecture 15	2012‑11‑30	12/13 PSI - Quantum Field Theory 2	Course	View details
Universal driven dynamics near phase transitions : Kibble-Zurek ramps with and without an order parameter	2012‑11‑29	Quantum Matter	Scientific Series	View details
Fractional quantum Hall effect and tunable interactions	2012‑11‑29	Quantum Matter	Scientific Series	View details
Fractional Chern Insulators	2012‑11‑29	Quantum Matter	Scientific Series	View details
Statistical Mechanics - Lecture 14	2012‑11‑29	12/13 PSI - Statistical Mechanics	Course	View details
Quantum Field Theory 2 - Lecture 14	2012‑11‑29	12/13 PSI - Quantum Field Theory 2	Course	View details
Dyon condensation in topological Mott insulators	2012‑11‑28	Quantum Matter	Scientific Series	View details
Wiring up Quantum Systems: Fun with Artificial Atoms and Microwave Photons	2012‑11‑28	Colloquium	Scientific Series	View details
12/13 PSI Researcher Presentation	2012‑11‑28	12/13 PSI Researcher Presentations	Course	View details

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Format results

Amplitude mode of the d-density wave state and its relevance to high-Tc cuprates

Statistical Mechanics - Lecture 15

Beyond the Search for Majorana

Quantum Field Theory 2 - Lecture 15

Universal driven dynamics near phase transitions : Kibble-Zurek ramps with and without an order parameter

Fractional quantum Hall effect and tunable interactions

Fractional Chern Insulators

Statistical Mechanics - Lecture 14

Quantum Field Theory 2 - Lecture 14

Dyon condensation in topological Mott insulators

Wiring up Quantum Systems: Fun with Artificial Atoms and Microwave Photons

12/13 PSI Researcher Presentation

Amplitude mode of the d-density wave state and its relevance to high-Tc cuprates

Statistical Mechanics - Lecture 15

Beyond the Search for Majorana

Quantum Field Theory 2 - Lecture 15

Universal driven dynamics near phase transitions : Kibble-Zurek ramps with and without an order parameter

Fractional quantum Hall effect and tunable interactions

Fractional Chern Insulators

Statistical Mechanics - Lecture 14

Quantum Field Theory 2 - Lecture 14

Dyon condensation in topological Mott insulators

Wiring up Quantum Systems: Fun with Artificial Atoms and Microwave Photons

12/13 PSI Researcher Presentation