Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session B1: Effect of Interactions in the Relaxation Dynamics and the Expansion of Ultracold Gases |
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Chair: Maxim Olshanii, University of Massachusetts at Boston Room: 200A |
Tuesday, June 4, 2013 10:30AM - 11:00AM |
B1.00001: The onset of thermalization in nearly integrable 1D Bose gases Invited Speaker: David Weiss |
Tuesday, June 4, 2013 11:00AM - 11:30AM |
B1.00002: Releasing the trapped 1d Bose gas: from integrability and renormalization to Generalized Gibbs ensembles Invited Speaker: Jean-S\'ebastien Caux In this talk, we consider the out-of-equilibrium evolution of a one-dimensional bosonic gas (as described by the Lieb-Liniger model) after release from a parabolic trapping potential. We present a new method based on combining the theory of integrable models with numerical renormalization, which allows to reconstruct the post-quench dynamics of the gas all the way to infinite time. We also present a framework by which the generalized Gibbs ensemble, which has been suggested as the effective theory governing this dynamics, can be explicitly constructed. We compare predictions for reequilibration from this ensemble against the long-time dynamics observed using our method. [Preview Abstract] |
Tuesday, June 4, 2013 11:30AM - 12:00PM |
B1.00003: Fermionic and Bosonic transport in homogeneous optical lattices Invited Speaker: Ulrich Schneider Out-of-equilibrium dynamics of interacting quantum systems present one of the hardest problems in many-body theory, harder than predicting static properties such as e.g. the nature of their ground states. At the same time, transport properties are among the defining characteristics of many important phases in condensed-matter physics, the most prominent example being the electrical conductivity, which, for example, allows one to distinguish normal conductors from insulators or superconductors. Ultracold atoms in optical lattices offer the possibility to study transport and out-of-equilibrium phenomena in a clean and well-controlled environment and can therefore act as a quantum simulator for condensed-matter systems. In this talk I will discuss our experimental studies on the expansion of initially confined quantum gases of either fermionic [1] or bosonic [2] atoms in the lowest band of a homogeneous optical lattice in various dimensions. For non-interacting atoms, we always observe ballistic transport, independent of the dimension. In two dimensions, already small interactions dramatically reduce the observed expansion velocity and give rise to almost bimodal density distributions containing a diffusive core. These dynamics are independent of the sign of the interaction, revealing a novel dynamic symmetry of the Hubbard model [1]. In the bosonic case, dimensionality has a crucial influence, since, in contrast to higher dimensions, one-dimensional bosonic systems expand ballistically also in the strongly interacting hard-core limit. Individually controlling the lattice depths along two directions has allowed us to observe a gradual crossover from ballistic to diffusive expansions in the hard-core limit [2]. \\[4pt] [1] U. Schneider et al., Nature Physics 8, 213 (2012)\\[0pt] [2] J.P. Ronzheimer et al., ArXiv:1301.5329 [Preview Abstract] |
Tuesday, June 4, 2013 12:00PM - 12:30PM |
B1.00004: Expansion dynamics of interacting bosons and fermions in one dimensional optical lattices Invited Speaker: Fabian Heidrich-Meisner This talk will provide an overview over the fascinating phenomena that can be encountered in the sudden expansion of interacting fermions or bosons in a lattice, starting from a trapped gas of particles. We simulate the dynamics using the time-dependent density matrix renormalization group method. In the transient regime, the expansion can dramatically alter correlations. I will discuss the dynamical emergence of coherence [1] and the quantum distillation mechanism [2]. The latter results in a spatial separation of repulsively or attractively bound pairs from unbound particles, which can be used to dynamically purify a band insulator [2]. Another topical example is the expansion of a spin-imbalanced gas, starting from the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state [3], relevant in the context of a recent experiment on 1D FFLO states [4]. In this case, the transient dynamics completely destroy the FFLO correlations. Nevertheless, experimentally accessible quantities may still preserve information on the initial state. First, the expansion velocity is sensitive to the presence of a Mott-insulator in the initial state [4]. Second, we argue that the asymptotic momentum distributions of integrable models are constrained by non-trivial integrals of motion [3].\\[4pt] [1] Heidrich-Meisner et al., Phys. Rev. A 78, 013620 (2008)\newline [2] Heidrich-Meisner et al., Phys. Rev. A 80, 041603(R) (2009)\newline [3] Bolech et al., Phys. Rev. Lett. 109, 110602 (2012)\newline [4] Liao et al. Nature 467, 567 (2010)\newline [5] Langer et al., Phys. Rev. A 85, 043618 (2012) [Preview Abstract] |
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