Quantum Matter

439 talks

S021

Collection TypeSeries

Displaying 325 - 336 of 439

Quantum criticality in SU(N) anti-ferromagnets: general strategies to circumvent the sign problem

Ribhu Kaul University of Kentucky
April 22, 2014

PIRSA:14040083
Condensed Matter
The unitary Fermi gas across the superfluid transition

Olga Goulko University of Massachusetts Amherst
April 04, 2014

PIRSA:14040119
Condensed Matter
Fibonacci Anyons From Abelian Bilayer Quantum Hall States

Abolhassan Vaezi Cornell University
April 01, 2014

PIRSA:14040120
Condensed Matter
Are superselection rules fundamental?

Robert Spekkens Perimeter Institute for Theoretical Physics
March 14, 2014

PIRSA:14030114
Condensed Matter
DMRG Analysis of Mobile Impurities and Orbital-selective Mott Phases

Julian (Jose) Rincon Universidad de los Andes
March 12, 2014

PIRSA:14030117
Condensed Matter
Exact holographic mapping and emergent space-time geometry

Xiaoliang Qi Stanford University
March 11, 2014

PIRSA:14030107
Condensed Matter
Numerical detection of symmetry protected and symmetry enriched topological phases

Frank Pollmann Max Planck Institute for Physics, Munich (Werner-Heisenberg-Institut)
February 25, 2014

PIRSA:14020140
Condensed Matter
Quantum Many-body Dynamics with Matrix Product States

Martin Ganahl Sandbox AQ
February 24, 2014

PIRSA:14020156
Cosmology

Condensed Matter
The emergent of the chiral spin liquid in kagome Heisenberg model

Dong-Ning Sheng California State University, Northridge
February 20, 2014

PIRSA:14020149
Condensed Matter
Paying the price of naturalness with a supersymmetric twin Higgs

Kiel Howe Stanford University
January 21, 2014

PIRSA:14010105
Condensed Matter
A lattice non-perturbative definition of chiral fermion/gauge theory from Topological Order

Juven Wang Harvard University
December 13, 2013

PIRSA:13120069
Condensed Matter
Symmetry Enriched Quantum Spin Ices On the Pyrochlore Lattice

Gang Chen Fudan University
December 06, 2013

PIRSA:13120055
Condensed Matter

Quantum criticality in SU(N) anti-ferromagnets: general strategies to circumvent the sign problem

Ribhu Kaul University of Kentucky
April 22, 2014

PIRSA:14040083
Condensed Matter
In the first part of the seminar, I will describe a general approach to write down a large family of model SU(N) anti-ferromagnets that do not suffer from the sign problem. In the second half I will show how such Hamiltonians are useful for the study of deconfined quantum critical points and possibly other exotic physics.
The unitary Fermi gas across the superfluid transition

Olga Goulko University of Massachusetts Amherst
April 04, 2014

PIRSA:14040119
Condensed Matter
Quantum Monte Carlo is a versatile tool for studying strongly interacting theories in condensed matter physics from first principles. A prominent example is the unitary Fermi gas: a two-component system of fermions interacting with divergent scattering length. I will present numerical results for different properties of the homogeneous, spin-balanced unitary Fermi gas across the superfluid transition, such as the critical temperature, the equation of state and the temperature dependence of the contact density. Our values show good agreement with recent experimental data.
Fibonacci Anyons From Abelian Bilayer Quantum Hall States

Abolhassan Vaezi Cornell University
April 01, 2014

PIRSA:14040120
Condensed Matter
The possibility of realizing non-Abelian statistics and utilizing it for topological quantum computation (TQC) has generated widespread interest. However, the non-Abelian statistics that can be realized in most accessible proposals is not powerful enough for universal TQC. In this talk, I consider a simple bilayer fractional quantum Hall (FQH) system with the 1/3 Laughlin state in each layer, in the presence of interlayer tunneling. I show that interlayer tunneling can drive a continuous phase transition to an exotic non-Abelian state that contains the famous `Fibonacci' anyon, whose non-Abelian statistics is powerful enough for universal TQC. The analysis that I will present towards this result rests on startling agreements from a variety of distinct methods, including thin torus limits, effective field theories, and coupled wire constructions.

Next, I discuss the experimental aspects of our proposal and potential probes for the Fibonacci phase. I show that the charge gap remains open at the phase transition while the neutral gap closes. This raises the question of whether these exotic phases may have already been realized at nu=2/3 in bilayers, as past experiments may not have definitively ruled them out. Finally, I will discuss about the generalizations to multi-layer states as well as the duality between the interlayer pairing and interlayer tunneling problems.

Reference: arXiv:1403.3383
Are superselection rules fundamental?

Robert Spekkens Perimeter Institute for Theoretical Physics
March 14, 2014

PIRSA:14030114
Condensed Matter
Superselection rules in quantum theory assert the impossibility of preparing coherent superpositions of certain conserved quantities. For instance, it is commonly presumed that there is a superselection rule for charge and for baryon number, as well as a "univalence superselection rule" forbidding a coherent superposition of a fermion and a boson. I will show how many superselection rules can be effectively lifted using a reference frame for the variable that is conjugate to the conserved quantity. I will also discuss subtleties related to the univalence superselection rule.
DMRG Analysis of Mobile Impurities and Orbital-selective Mott Phases

Julian (Jose) Rincon Universidad de los Andes
March 12, 2014

PIRSA:14030117
Condensed Matter
Exact holographic mapping and emergent space-time geometry

Xiaoliang Qi Stanford University
March 11, 2014

PIRSA:14030107
Condensed Matter
Holographic duality is a duality between quantum many-body systems (boundary) and gravity systems with one additional spatial dimension (bulk). In this talk, I will describe a new approach to holographic duality for lattice systems, called the exact holographic mapping. The key idea of this approach can be summarized by two points: 1) The bulk theory is nothing but the boundary theory viewed in a different basis. 2) Space-time geometry is determined by the structure of correlations and quantum entanglement in a quantum state. For free fermion boundary theories, I will show how different bulk geometries including AdS space, black holes and worm-holes emerge. I will also discuss the generalization of this approach in more generic interacting systems.
Numerical detection of symmetry protected and symmetry enriched topological phases

Frank Pollmann Max Planck Institute for Physics, Munich (Werner-Heisenberg-Institut)
February 25, 2014

PIRSA:14020140
Condensed Matter
A topological phase is a phase of matter which cannot be characterized by a local order parameter. We first introduce non-local order parameters that can detect symmetry protected topological (SPT) phases in 1D systems and then show how to generalize the idea to detect symmetry enriched topological (SET) phases in 2D. SET phases are new structures that occur in topologically ordered systems in the presence of symmetries. We introduce simple methods to detect the SET order directly from a complete set of topologically degenerate ground state wave functions. We first show how to directly determine the characteristic symmetry fractionalization of the quasiparticles from the reduced density matrix of the minimally entangled states. Second, we show how a simple generalization of a non-local order parameter can be measured to detect SETs. The usefulness of the proposed approached is demonstrated by examining two concrete model states which exhibit SET: (i) a spin-1 model on the honeycomb lattice and (ii) the resonating valence bond state on a kagome lattice. We conclude that the spin-1 model and the RVB state are in the same SET phases.
Quantum Many-body Dynamics with Matrix Product States

Martin Ganahl Sandbox AQ
February 24, 2014

PIRSA:14020156
Cosmology

Condensed Matter
The talk is divided into two parts: in the first, I will talk about dynamics of far-from equilibrium initial states in different lattice models. I will present results of quench dynamics of the XXZ-Heisenberg magnet, where interesting physics emerges after quenching the system. Then I will present results for scattering of solitonic objects in different integrable and non-integrable lattice models. In the second part, I will talk about dynamics of impurity systems. There I will talk about how impurity spectral functions can be calculated using the Chebyshev technique, and how MPS can serve as a high resolution impurity solver for Dynamical Mean-Field Theory. Finally, I will show some results for steady-state currents through a quantum dot device.
The emergent of the chiral spin liquid in kagome Heisenberg model

Dong-Ning Sheng California State University, Northridge
February 20, 2014

PIRSA:14020149
Condensed Matter
The quantum spin liquid is an emergent new state of matter, which has attracted a lot of recent attention. In particular, the time reversal symmetry broken spin liquid (Kalmeyer et. al. and Wen et. al.), characterized by the chiral ordering and fractionalized quasi-particle as a realization of the fractional quantum Hall state had been proposed for more than 20 years, but never identified as the true ground state in any more generic (e.g. Heisenberg spin exchange) models with time reversal symmetry. Here I will report two concrete examples where chiral spin liquid (CSL) emerge for a range of parameter space for kagome J1-J2-J3 (three nearest neighbors) model based on accurate density matrix renormalization group (DMRG) simulations. We identify long-range chiral ordering, ground state degeneracy, characteristic entanglement spectra, and the fractionalized topological Chern number to establish the topological state in such a system as the long-sought CSL. We further explicitly extract the modular matrix, which captures all the information of the fractional statistics of the quasi-particles in the system. I will also discuss the close relation of our model to some frustrated kagome antiferromagnets, and make a conjecture that J1 kagome model is near an unconventional critical point. I will conclude the talk with some discussions of the open directions.
Paying the price of naturalness with a supersymmetric twin Higgs

Kiel Howe Stanford University
January 21, 2014

PIRSA:14010105
Condensed Matter
What is the price of naturalness? In minimal extensions of the standard model, stringent limits on new colored particles and measurements of Higgs properties from the LHC severely challenge the hypothesis of naturalness of the electroweak scale. However, these measurements also provide unprecedented guidance in exploring non-minimal models of new electroweak physics. The supersymmetric twin Higgs provides a concrete example where few-percent level tuning remains compatible with superpartner limits and Higgs physics as well as gauge coupling unification and other successes of the MSSM. Studying such models in detail is crucial to understanding the role naturalness will play as a motivating principle for future searches at the 13 TeV LHC and beyond.
A lattice non-perturbative definition of chiral fermion/gauge theory from Topological Order

Juven Wang Harvard University
December 13, 2013

PIRSA:13120069
Condensed Matter
A non-perturbative definition of anomaly-free chiral fermions and bosons in 1+1D spacetime as finite quantum systems on 1D lattice is proposed. In particular, any 1+1D anomaly-free chiral matter theory can be defined as finite quantum systems on 1D lattice with on-site symmetry, if we include strong interactions between matter fields. Our approach provides another way, apart from Ginsparg-Wilson fermions approach, to avoid the fermion-doubling challenge. In general, using the defining connection between gauge anomalies and the symmetry-protected topological orders, we propose that any truly anomaly-free chiral gauge theory can be non-perturbatively defined by putting it on a lattice in the same dimension. As an additional remark, we conjecture/prove the equivalence relation between 't Hooft anomaly matching conditions and the boundary fully gapping rules.
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.

Title	Speaker(s)	Date	Talk Type	Info
Quantum criticality in SU(N) anti-ferromagnets: general strategies to circumvent the sign problem	Ribhu Kaul	2014-04-22	Scientific Series	View details
The unitary Fermi gas across the superfluid transition	Olga Goulko	2014-04-04	Scientific Series	View details
Fibonacci Anyons From Abelian Bilayer Quantum Hall States	Abolhassan Vaezi	2014-04-01	Scientific Series	View details
Are superselection rules fundamental?	Robert Spekkens	2014-03-14	Scientific Series	View details
DMRG Analysis of Mobile Impurities and Orbital-selective Mott Phases	Julian (Jose) Rincon	2014-03-12	Scientific Series	View details
Exact holographic mapping and emergent space-time geometry	Xiaoliang Qi	2014-03-11	Scientific Series	View details
Numerical detection of symmetry protected and symmetry enriched topological phases	Frank Pollmann	2014-02-25	Scientific Series	View details
Quantum Many-body Dynamics with Matrix Product States	Martin Ganahl	2014-02-24	Scientific Series	View details
The emergent of the chiral spin liquid in kagome Heisenberg model	Dong-Ning Sheng	2014-02-20	Scientific Series	View details
Paying the price of naturalness with a supersymmetric twin Higgs	Kiel Howe	2014-01-21	Scientific Series	View details
A lattice non-perturbative definition of chiral fermion/gauge theory from Topological Order	Juven Wang	2013-12-13	Scientific Series	View details
Symmetry Enriched Quantum Spin Ices On the Pyrochlore Lattice	Gang Chen	2013-12-06	Scientific Series	View details

Quantum Matter

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