Condensed Matter

Displaying 1009 - 1020 of 1218

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 Physics

Condensed Matter
Characterizing topological order form a microscopic lattice Hamiltonian

Lukasz Cincio Los Alamos National Laboratory
May 09, 2013

PIRSA:13050042
Quantum Physics

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
High Energy Physics

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
3D topological lattice models with topologically ordered surface states

Fiona Burnell University of Minnesota
May 07, 2013

PIRSA:13050032
Condensed Matter
Majorana Ghosts: From topological superconductor to the origin of neutrino mass, three generations and their mass mixing

Zheng-Cheng Gu Chinese University of Hong Kong
May 07, 2013

PIRSA:13050052
Condensed Matter
Fractionalizing Majorana fermions: non-abelian statistics on the edges of abelian quantum Hall states

Erez Berg Weizmann Institute of Science
May 07, 2013

PIRSA:13050029
Condensed Matter

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 Physics

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 Physics

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
High Energy Physics

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.
3D topological lattice models with topologically ordered surface states

Fiona Burnell University of Minnesota
May 07, 2013

PIRSA:13050032
Condensed Matter
I will discuss a family of solvable 3D lattice models that have a ``trivial" bulk, in which all excitations are confined, but exhibit topologically ordered surface states. I will discuss perturbations to these models that can drive a phase transition in which some of these excitations become deconfined, driving the system into a phase with bulk topological order.
Majorana Ghosts: From topological superconductor to the origin of neutrino mass, three generations and their mass mixing

Zheng-Cheng Gu Chinese University of Hong Kong
May 07, 2013

PIRSA:13050052
Condensed Matter
The existence of three generations of neutrinos and their mass mixing is a deep mystery of our universe. On the other hand, Majorana's elegant work on the real solution of Dirac equation predicted the existence of Majorana particles in our nature, unfortunately, these Majorana particles have never been observed. In this talk, I will begin with a simple 1D condensed matter model which realizes a T^2=-1 time reversal symmetry protected superconductors and then discuss the physical property of its boundary Majorana zero modes. It is shown that these Majorana zero modes realize a T^4=-1 time reversal doubelets and carry 1/4 spin. Such a simple observation motivates us to revisit the CPT symmetry of those ghost particles--neutrinos by assuming that they are Majorana zero modes. Interestingly, we find that a topological Majorana particle will realize a P^4=-1 parity symmetry as well. It even realizes a nontrivial C^4=-1 charge conjugation symmetry, which is a big surprise from a usual perspective that the charge conjugation symmetry for a Majorana particle is trivial. Indeed, such a C^4=-1 charge conjugation symmetry is a Z_2 gauge symmetry and its spontaneously breaking leads to the origin of neutrino mass. We further attribute the origin of three generations of neutrinos to three distinguishable types of topological Majorana zero modes protected by CPT symmetry. Such an assumption leads to an S3 symmetry in the generation space and uniquely determines the mass mixing matrix with no adjustable parameters! In the absence of CP violation, we derive \theta_12=32degree, \theta_23=45degree and \theta_13=0degree, which is intrinsically closed to the current experimental results. We further predict an exact mass ratio of the three mass eigenstate with m_1/m_3~m_2/m_3=3/\sqrt{5}.
Fractionalizing Majorana fermions: non-abelian statistics on the edges of abelian quantum Hall states

Erez Berg Weizmann Institute of Science
May 07, 2013

PIRSA:13050029
Condensed Matter
We study the non-abelian statistics characterizing systems where counter-propagating gapless modes on the edges of fractional quantum Hall states are gapped by proximity-coupling to superconductors and ferromagnets. The most transparent example is that of a fractional quantum spin Hall state, in which electrons of one spin direction occupy a fractional quantum Hall state of $\nu= 1/m$, while electrons of the opposite spin occupy a similar state with $\nu = -1/m$. However, we also propose other examples of such systems, which are easier to realize experimentally. We find that each interface between a region on the edge coupled to a superconductor and a region coupled to a ferromagnet corresponds to a non-abelian anyon of quantum dimension $\sqrt{2m}$. We calculate the unitary transformations that are associated with braiding of these anyons, and show that they are able to realize a richer set of non-abelian representations of the braid group than the set realized by non-abelian anyons based on Majorana fermions. We carry out this calculation both explicitly and by applying general considerations. Finally, we show that topological manipulations with these anyons cannot realize universal quantum computation.

Title	Speaker(s)	Date	Talk Type	Info link
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
3D topological lattice models with topologically ordered surface states	Fiona Burnell	2013-05-07	Conference	View details
Majorana Ghosts: From topological superconductor to the origin of neutrino mass, three generations and their mass mixing	Zheng-Cheng Gu	2013-05-07	Conference	View details
Fractionalizing Majorana fermions: non-abelian statistics on the edges of abelian quantum Hall states	Erez Berg	2013-05-07	Conference	View details

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Geometry and the entanglement spectrum in the fractional quantum Hall effect.

Topological Phases with of Bosons with Short Range Quantum Entanglement

Spin-orbital quantum liquid on the honeycomb lattice

Characterizing topological order form a microscopic lattice Hamiltonian

Quantum Spin Liquids,Density Matrix Renormalization Group, and Entanglement

Searching for Spin Liquids

Entangled states of quantum matter

Holographic insights into quantum critical transport: from branes to Bose-Hubbard

Thermodynamical Property of Entanglement Entropy for Excited States

3D topological lattice models with topologically ordered surface states

Majorana Ghosts: From topological superconductor to the origin of neutrino mass, three generations and their mass mixing

Fractionalizing Majorana fermions: non-abelian statistics on the edges of abelian quantum Hall states

Geometry and the entanglement spectrum in the fractional quantum Hall effect.

Topological Phases with of Bosons with Short Range Quantum Entanglement

Spin-orbital quantum liquid on the honeycomb lattice

Characterizing topological order form a microscopic lattice Hamiltonian

Quantum Spin Liquids,Density Matrix Renormalization Group, and Entanglement

Searching for Spin Liquids

Entangled states of quantum matter

Holographic insights into quantum critical transport: from branes to Bose-Hubbard

Thermodynamical Property of Entanglement Entropy for Excited States

3D topological lattice models with topologically ordered surface states

Majorana Ghosts: From topological superconductor to the origin of neutrino mass, three generations and their mass mixing

Fractionalizing Majorana fermions: non-abelian statistics on the edges of abelian quantum Hall states