Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session V4: Dynamics and Non-equilbrium Phenomena in Optical Lattices |
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Sponsoring Units: DAMOP Chair: Eugene Demler, Harvard University Room: Baltimore Convention Center 308 |
Thursday, March 16, 2006 11:15AM - 11:51AM |
V4.00001: Phase coherence, visibility, and the signatures of superfluid-Mott and metal-Mott insulator transitions on optical lattices Invited Speaker: Experiments are revealing, with increasing precision, details of the Mott insulating (MI) and superfluid (SF) phases of atomic condensates confined on optical lattices. Recently, details of the transition between the MI and the SF phases, as the lattice potential is changed, were examined by studying the visibility and phase coherence of the condensate. Reproducible kinks were observed in the visibility as the lattice potential was made deeper and the system moved into the MI phase. These kinks were interpreted as being due to the formation of the Mott region. We shall first review briefly the properties of the various phases of this system and how it makes the transition from SF to MI. Then we present a detailed Quantum Monte Carlo study of the visibility and other physical quantities as Mott domains begin to form. We show that as the lattice potential gets deeper and Mott domains become well established, the evolution of the system stalls: the density profile stops evolving for a substantial range of values of the lattice potential. As a consequence, the evolution of several other quantities also stalls and the visibility kink is produced. We offer an explanation of this behavior. We then extend our study to the formation of Mott domains in fermionic atoms on confined one-dimensional optical lattices. We find a new property of the metal--Mott insulator transition in a trap. The sum of kinetic and interaction energies exhibits minima when Mott domains appear in the system. In addition, we examine the derivatives of the kinetic and interaction energies, and of their sum, which display clear signatures of the Mott transition. We discuss the relevance of these findings to time of flight experiments that could allow the detection of the metal--Mott-insulator transition in confined fermions on optical lattices. [Preview Abstract] |
Thursday, March 16, 2006 11:51AM - 12:27PM |
V4.00002: Superfluid-Insulator Transition in a Moving System of Interacting Bosons Invited Speaker: Cold atomic systems with their high tunability and nearly perfect isolation from environment give an exciting possibility to address non-equilibrium problems, where both quantumand dynamic effects are important. In this talk I describe a moving system of interacting bosons in a periodic optical lattice potential and generalize the conventional superfluid-Mott insulator transition to this highly non-equilibrium situation. I will discuss implications of our results to recent and future experiments. [Preview Abstract] |
Thursday, March 16, 2006 12:27PM - 1:03PM |
V4.00003: Non-equilibrium one-dimensional Bose gases Invited Speaker: I will describe the preparation and time evolution of arrays of trapped one-dimensional Bose gases with highly non-equilibrium momentum distributions. We observe negligible thermalization, in both the strong and intermediate coupling regimes, even after each atom has undergone thousands of collisions. These experiments can be understood as quantum mechanical versions of Newton's cradle, with hundreds of particles simply exchanging specific momentum values. The absence of thermalization demonstrates nearly integrable dynamics, which is a theoretical rarity and an experimental first for many-body systems with many degrees of freedom. By allowing tunnelling among the tubes, we can continuously change the collisions from one-dimensional to three-dimensional. We have thus been able to study the onset of thermalization in a many-body system. [Preview Abstract] |
Thursday, March 16, 2006 1:03PM - 1:39PM |
V4.00004: Equilibrium and nonequilibrium properties of Tonks-Girardeau gases confined on optical lattices Invited Speaker: In this talk we discuss recent exact results for the in and out of equilibrium properties of Tonks-Girardeau (TG) bosons confined on one-dimensional lattices. The TG gas, introduced theoretically more than 40 years ago, has been recently realized in experiments with ultracold quantum gases loaded on optical lattices. We show that universal quasi-long range correlations are present in the ground state of trapped TG gases. These correlations account for the existence of quasi-condensates whose occupation scales proportionally to the square root of the number of particles in the trap. We find that when such systems are allowed to expand, by turning off the confining potential, their momentum distribution function rapidly approaches the one of noninteracting fermions. Remarkably, no loss in coherence is observed in the system as reflected by a large occupation of the quasi-condensates. We also study the expansion of TG gases starting their evolution from a pure Mott insulating state with one particle per lattice site. In this case quasi-long range correlations develop dynamically, and lead to the formation of traveling quasicondensates with a momentum determined by the underlying lattice. This effect could be used to create atom lasers with full control of the wavelength. Finally, we analyze the dipolar oscillations of TG gases in the combination harmonic trap - optical lattice. We show that damping is always present, and produces dramatic effects in the momentum distribution of the bosons. These effects are similar to the ones that would create a finite temperature in the system. In the presence of Mott insulating domains, the dipolar oscillations of the TG gas are overdamped and the center of mass barely moves from its initial displaced position. [Preview Abstract] |
Thursday, March 16, 2006 1:39PM - 2:15PM |
V4.00005: One-dimensional spin-polarized fermions Invited Speaker: The fermionic Tonks-Girardeau (FTG)gas is a spin-aligned one-dimensional Fermi gas with infinitely strong attractive zero-range odd-wave interactions. This model describes experiments on ultracold atomic gases subjected to tight quasi-1D waveguides and close to a Feshbach resonance. I will report on the recent investigations of the FTG gas under different trapping conditions (harmonic and ring traps) and in the presence of disorder. In particular I will discuss the pairing properties of this gas, the possibility of metastable current flows and the response to rotation. Finally, for a gas initially under harmonic confinement I will show that during an expansion the momentum distribution undergoes a ``dynamical bosonization,'' i.e., approaches the one of an ideal Bose gas, without violating the Pauli exclusion principle. [Preview Abstract] |
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