Condensed Matter

Condensed matter physics is the branch of physics that studies systems of very large numbers of particles in a condensed state, like solids or liquids. Condensed matter physics wants to answer questions like: why is a material magnetic? Or why is it insulating or conducting? Or new, exciting questions like: what materials are good to make a reliable quantum computer? Can we describe gravity as the behavior of a material? The behavior of a system with many particles is very different from that of its individual particles. We say that the laws of many body physics are emergent or collective. Emergence explains the beauty of physics laws.

Displaying 1033 - 1044 of 1245

Momentum polarization: an entanglement measure of topological spin and chiral central charge

Xiaoliang Qi Stanford University
May 10, 2013

PIRSA:13050047
Condensed Matter
Twisted Symmetry in Tensor Network States and Topological Order

Oliver Buerschaper Multiverse Computing (Germany)
May 10, 2013

PIRSA:13050048
Quantum Information

Condensed Matter
Defects in Topologically Ordered Quantum Matter

Maissam Barkeshli University of California, Santa Barbara
May 10, 2013

PIRSA:13050053
Condensed Matter
Geometry and the entanglement spectrum in the fractional quantum Hall effect.
May 10, 2013

PIRSA:13050049
Condensed Matter
Topological Phases with of Bosons with Short Range Quantum Entanglement

Ashvin Vishwanath Harvard University
May 10, 2013

PIRSA:13050046
Condensed Matter
Spin-orbital quantum liquid on the honeycomb lattice

Philippe Corboz Universiteit van Amsterdam
May 09, 2013

PIRSA:13050045
Quantum Information

Condensed Matter
Characterizing topological order form a microscopic lattice Hamiltonian

Lukasz Cincio Los Alamos National Laboratory
May 09, 2013

PIRSA:13050042
Quantum Information

Condensed Matter
Quantum Spin Liquids,Density Matrix Renormalization Group, and Entanglement

Leon Balents University of California, Santa Barbara
May 09, 2013

PIRSA:13050040
Condensed Matter
Searching for Spin Liquids

Steven White University of California, Irvine
May 09, 2013

PIRSA:13050039
Quantum Fields and Strings

Condensed Matter
Entangled states of quantum matter

Subir Sachdev Harvard University
May 08, 2013

PIRSA:13050038
Condensed Matter
Holographic insights into quantum critical transport: from branes to Bose-Hubbard
May 08, 2013

PIRSA:13050037
Condensed Matter
Thermodynamical Property of Entanglement Entropy for Excited States

Tadashi Takayanagi Yukawa Institute for Theoretical Physics
May 08, 2013

PIRSA:13050034
Condensed Matter

Momentum polarization: an entanglement measure of topological spin and chiral central charge

Xiaoliang Qi Stanford University
May 10, 2013

PIRSA:13050047
Condensed Matter
Topologically ordered states are quantum states of matter with topological ground state degeneracy and quasi-particles carrying fractional quantum numbers and fractional statistics. The topological spin is an important property of a topological quasi-particle, which is the Berry phase obtained in the adiabatic self-rotation of the quasi-particle by . For chiral topological states with robust chiral edge states, another fundamental topological property is the edge state chiral central charge . In this paper we propose a new approach to compute the topological spin and chiral central charge in lattice models by defining a new quantity named as the momentum polarization. Momentum polarization is defined on the cylinder geometry as a universal subleading term in the average value of a "partial translation operator". We show that the momentum polarization is a quantum entanglement property which can be computed from the reduced density matrix, and our analytic derivation based on edge conformal field theory shows that the momentum polarization measures the combination of topological spin and central charge. Numerical results are obtained for two example systems, the non-Abelian phase of the honeycomb lattice Kitaev model, and the Laughlin state of a fractional Chern insulator described by a variational Monte Carlo wavefunction. The numerical results verifies the analytic formula with high accuracy, and further suggests that this result remains robust even when the edge states cannot be described by a conformal field theory. Our result provides a new efficient approach to characterize and identify topological states of matter from finite size numerics.
Twisted Symmetry in Tensor Network States and Topological Order

Oliver Buerschaper Multiverse Computing (Germany)
May 10, 2013

PIRSA:13050048
Quantum Information

Condensed Matter
Defects in Topologically Ordered Quantum Matter

Maissam Barkeshli University of California, Santa Barbara
May 10, 2013

PIRSA:13050053
Condensed Matter
I will discuss recent advances in our understanding of extrinsic defects in topologically ordered states. These include line defects, where I will discuss recent developments in the classification of gapped boundaries between Abelian topological states, and various kinds of point defects, which host a rich set of topological physics. The extrinsic point defects provide a new way of realizing topologically protected ground state degeneracies, they carry projective non-abelian statistics even in an Abelian topological state and provide a new path towards universal topological quantum computation, they host a general class of topologically protected "parafermion" zero modes, and they provide an avenue towards distinguishing various symmetry-enriched topological phases. I will discuss several novel physical realizations of such point defects, and also a recent experimental proposal to realize such defects in conventional bilayer fractional quantum Hall systems.
Geometry and the entanglement spectrum in the fractional quantum Hall effect.
May 10, 2013

PIRSA:13050049
Condensed Matter
Fractional quantum hall states with nu = p/q have a characteristic geometry defined by the electric quadrupole moment of the neutral composite boson that is formed by "flux attachment" of q "flux quanta" (guiding-center orbitals) to p charged particles. This characterizes the "Hall viscosity". For FQHE states described by a conformal field theory with a Euclidean metric g_ab, the quadrupole moment is proportional to the "guiding-center spin" of the composite boson and the inverse metric. The geometry gives rise to dipole moments at external edges or internal "orbital entanglement cuts", and can be seen in the entanglement spectrum.
Topological Phases with of Bosons with Short Range Quantum Entanglement

Ashvin Vishwanath Harvard University
May 10, 2013

PIRSA:13050046
Condensed Matter
Spin-orbital quantum liquid on the honeycomb lattice

Philippe Corboz Universiteit van Amsterdam
May 09, 2013

PIRSA:13050045
Quantum Information

Condensed Matter
The symmetric Kugel-Khomskii can be seen as a minimal model describing the interactions between spin and orbital degrees of freedom in certain transition-metal oxides with orbital degeneracy, and it is equivalent to the SU(4) Heisenberg model of four-color fermionic atoms. We present simulation results for this model on various two-dimensional lattices obtained with infinite projected-entangled pair states (iPEPS), an efficient variational tensor-network ansatz for two dimensional wave functions in the thermodynamic limit. We find a rich variety of exotic phases: while on the square and checkerboard lattices the ground state exhibits dimer-N\'eel order and plaquette order, respectively, quantum fluctuations on the honeycomb lattice destroy any order, giving rise to a spin-orbital liquid. Our results are supported from flavor-wave theory and exact diagonalization. Furthermore, the properties of the spin-orbital liquid state on the honeycomb lattice are accurately accounted for by a projected variational wave-function based on the pi-flux state of fermions on the honeycomb lattice at 1/4-filling. In that state, correlations are algebraic because of the presence of a Dirac point at the Fermi level, suggesting that the ground state is an algebraic spin-orbital liquid. This model provides a possible starting point to understand the recently discovered spin-orbital liquid behavior of Ba_3CuSb_2O_9. The present results also suggest to choose optical lattices with honeycomb geometry in the search for quantum liquids in ultra-cold four-color fermionic atoms.
Characterizing topological order form a microscopic lattice Hamiltonian

Lukasz Cincio Los Alamos National Laboratory
May 09, 2013

PIRSA:13050042
Quantum Information

Condensed Matter
In this talk I will show how to obtain a detailed characterization of the emergent topological order starting from microscopic Hamiltonian on a two dimensional lattice. A key step is to obtain a tensor network representation for a complete set of ground states of the Hamiltonian, ﬁrst on an inﬁnite cylinder and then on a ﬁnite torus. As an application of the method I will study lattice Hamiltonians that give rise to selected anyon models, namely chiral semion, Ising as well as Z_3 and Z_5 models.
Quantum Spin Liquids,Density Matrix Renormalization Group, and Entanglement

Leon Balents University of California, Santa Barbara
May 09, 2013

PIRSA:13050040
Condensed Matter
I will review recent work in our group using Density Matrix Renormalization Group (DMRG) to search for and study quantum spin liquid and topologically ordered states in two dimensional model Hamiltonians. This proves an efficient way to study these phases in semi-realistic situations. I will try to draw lessons from several studies and theoretical considerations.
Searching for Spin Liquids

Steven White University of California, Irvine
May 09, 2013

PIRSA:13050039
Quantum Fields and Strings

Condensed Matter
Entangled states of quantum matter

Subir Sachdev Harvard University
May 08, 2013

PIRSA:13050038
Condensed Matter
Theorists have been studying and classifying entanglement in many-particle quantum states for many years. In the past few years, experiments on such states have finally appeared, generating much excitement. I will describe experimental observations on magnetic insulators, ultracold atoms, and high temperature superconductors, and their invigorating influence on our theoretical understanding.
Holographic insights into quantum critical transport: from branes to Bose-Hubbard
May 08, 2013

PIRSA:13050037
Condensed Matter
We discuss the general features of charge transport of quantum critical points described by CFTs in 2+1D. Our main tool is the AdS/CFT correspondence, but we will make connections to standard field theory results and to recent quantum Monte Carlo data. We emphasize the importance of poles and zeros of the response functions. In the holographic setting, these are the discrete quasinormal modes of a black hole/brane; they map to the excitations of the CFT. We further describe the role of particle-vortex or S-duality on the conductivity, which is argued to obey two powerful sum rules.
References (with S. Sachdev): arXiv:1210.4166 (PRB 12); arXiv:1302.0847 (PRB 13)
Thermodynamical Property of Entanglement Entropy for Excited States

Tadashi Takayanagi Yukawa Institute for Theoretical Physics
May 08, 2013

PIRSA:13050034
Condensed Matter
We will point out that there is a universal thermodynamical property of entanglement entropy for excited states. We will derive this by using the AdS/CFT correspondence in any dimension. We will also directly confirm this property from direct field theoretic calculations in two dimensions. We will define a new quantity called entanglement density by taking derivatives of entanglement entropy with respect to the shape of subsystem. We will show that this quantity coincides with the energy density by taking the small subsystem limit and show that this is another equivalent statement of the thermodynamical property.

Title	Speaker(s)	Date	Talk Type	Info link
Momentum polarization: an entanglement measure of topological spin and chiral central charge	Xiaoliang Qi	2013-05-10	Conference	View details
Twisted Symmetry in Tensor Network States and Topological Order	Oliver Buerschaper	2013-05-10	Conference	View details
Defects in Topologically Ordered Quantum Matter	Maissam Barkeshli	2013-05-10	Conference	View details
Geometry and the entanglement spectrum in the fractional quantum Hall effect.		2013-05-10	Conference	View details
Topological Phases with of Bosons with Short Range Quantum Entanglement	Ashvin Vishwanath	2013-05-10	Conference	View details
Spin-orbital quantum liquid on the honeycomb lattice	Philippe Corboz	2013-05-09	Conference	View details
Characterizing topological order form a microscopic lattice Hamiltonian	Lukasz Cincio	2013-05-09	Conference	View details
Quantum Spin Liquids,Density Matrix Renormalization Group, and Entanglement	Leon Balents	2013-05-09	Conference	View details
Searching for Spin Liquids	Steven White	2013-05-09	Conference	View details
Entangled states of quantum matter	Subir Sachdev	2013-05-08	Scientific Series	View details
Holographic insights into quantum critical transport: from branes to Bose-Hubbard		2013-05-08	Conference	View details
Thermodynamical Property of Entanglement Entropy for Excited States	Tadashi Takayanagi	2013-05-08	Conference	View details

Condensed Matter

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