Quantum over breakfast Quantum over breakfast

Spring 2011

April 29

Fifth meeting

Posted on 04/27/2011

Science and Technology I, Room 306, 11am (+ lunch after noon)

QOB informal talk
Dr. Satyan Bhongale, GMU

Fermionic dipolar molecules on a square lattice
Recent trapped atom experiments are able to generate an ultra-cold gas of heteronuclear molecules with a sufficiently large dipole moment to allow for the occurrence of rich many-body physics leading to exotic quantum phases. A key role is played by the anisotropic and long range nature of the dipole-dipole interaction. We study the system of fermionic dipolar molecules in a 2D optical lattice. Previous studies for homogeneous configurations have revealed the possibility of s-wave CDW and the p-wave BCS phase. In our study we take an unbiased approach by following the functional RG technique. This method allows us to look at the flow of various channels as one approaches the Fermi surface in the RG sense. We find an intriguing interplay between the s-wave CDW and the p-wave superfluid phases.

April 15

Fourth meeting

Posted on 04/12/2011

Science and Technology I, Room 306, 11am (+ lunch after noon)

QOB informal talk
Dr. Bin Wang, University of Maryland

Time-Evolving-Block-Decimation Studies on Ultracold Atoms in 1D Optical Lattices
Time-Evolving-Block-Decimation (TEBD) algorithm is a powerful tool for the study of ground state and dynamical properties of quantum lattice models in one dimension. In this talk, I will introduce the basic ideas of the TEBD algorithm and its applications in two pieces of our recent work. In the first work, we study the ground state properties of a topological liquid phase in one dimension, which can be thought of as the gapless analog of the Haldane gapped phase of a spin-one Heisenberg chain. This novel phase, in principle, can be realized in a system of ultracold two-component fermionic dipolar gases in 1D optical lattice with strong two-body on-site loss. In the second work, TEBD algorithm is applied to study the non-equilibrium dynamics of 1D Bose-Hubbard model. Recently a set of experiments have used the development of a coherence peak at specific momenta in quenched Mott insulators to realize exotic superfluid-like states. We calculate the evolution of the momentum distribution following a Mott insulator to Superfluid quench and try to clarify the nature of the final states.

April 1

Third meeting

Posted on 03/29/2011

Science and Technology I, Room 306, 11am (+ lunch after noon)

QOB informal talk
Dr. Tanja Djuric, George Mason University

Topological insulators and superconductors
Superconductivity in a topological insulator can be induced by proximity effect. This generates effective attractive interactions between electrons in the topological insulator. In this talk I will discuss novel superconducting and insulating phases that appear in the phase diagram of a two-dimensional time-reversal invariant topological insulator with short-range attractive interactions.

March 11

Second meeting

Posted on 03/07/2011

Science and Technology I, Room 306, 11am (+ lunch after noon)

QOB visitor informal talk
Dr. Chris Varney, Georgetown University

Quantum Phase Transitions in Topological Insulators and Quantum Spin Liquids
Recent years have seen an explosion of interest in topological phases of matter, which are characterized by robust conducting edge states with the bulk of the material remaining an insulator. In the most well-studied examples of the topologically nontrivial insulators, interactions are considered to be irrelevant and the driven mechanism is a strong spin-orbit coupling or an external magnetic field. However, it has become increasingly important to discover and understand new mechanisms which could stabilize these exotic states of matter. In this talk, I will examine the role interactions play in a model for the Quantum Hall Effect. In particular, I will show that the interactions induce a phase transition from a topological insulator to a charge density wave. Experimental implications and exotic phases for hard-core bosons will also be discussed.

January 24

First meeting

Posted on 01/20/2011

Science and Technology I, Room 306, 1pm

QOB visitor informal talk
Prof. Markus Mueller, The Abdus Salam International Centre for Theoretical Physics, Trieste, Italy

Graphene: Relativistic, collision-dominated transport in a nearly perfect quantum liquid
Electrons and holes in clean graphene behave very much like a strongly coupled relativistic liquid. The thermo-electric transport properties of its interacting Dirac quasiparticles are rather special, being constrained by an emergent Lorentz covariance at hydrodynamic frequency scales. At small carrier density and high temperatures, graphene exhibits several signatures of a quantum critical system: an inelastic scattering rate determined only by temperature, minimal electrical and spin conductivities dominated by electron-hole friction, and a very low viscosity. The latter suggests the interesting possibility of turbulent current flow in clean samples. Also many other transport properties differ substantially form standard Fermi liquid characteristics. Closely analogous features are found in certain strongly coupled relativistic liquids such as the quark-gluon plasma, which served indeed as an inspiration for the study of the peculiar properties of graphene.