Regensburg 2025 – scientific programme

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SYQS: Symposium Nonequilibrium Collective Behavior in Open Classical and Quantum Systems

SYQS 1: Nonequilibrium Collective Behavior in Open Classical and Quantum Systems

SYQS 1.3: Invited Talk

Thursday, March 20, 2025, 16:00–16:30, H1

Nonequilibrium Dynamics of Disorder-Driven Ultracold Fermi Gases — •Artur Widera — University of Kaiserslautern-Landau, Department of Physics and state-research center OPTIMAS, 67663 Kaiserslautern, Germany

Ultracold quantum gases provide a unique platform to experimentally study many-body dynamics under precisely controlled external potentials and driving forces. In this talk, I will present recent results on the dynamics of an ultracold gas of spin-polarized fermionic lithium atoms subjected to a time-dependent disorder potential. For static disorder, we observe signatures of the well-known Anderson localization. In contrast, time-varying disorder with finite correlation time is expected to disrupt localization. Specifically, for weak disorder, we find that time-dependent disorder induces a transition in the transport behavior of the gas from normal diffusion to superdiffusion and eventually ballistic motion as the correlation time of the disorder decreases. This enhanced diffusion is well described by a stochastic Fermi acceleration model, where randomly fluctuating force fields drive the system. Interestingly, for strong disorder, normal diffusion persists over a broad range of disorder correlation times despite the time-varying potential. We attribute this resilience to the continued presence of destructive interference as quantified by the localized fraction of atoms, which remains intact even under the influence of time-dependent disorder. These results point toward a nonequilibrium phase transition between localized and diffusive regimes in this driven system.

Keywords: Ultracold quantum gases; Time-dependent optical disorder; Anderson localization; Stochastic Fermi acceleration