Freiburg 2024 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 24: Poster II

Q 24.26: Poster

Tuesday, March 12, 2024, 17:00–19:00, KG I Foyer

Fermi accelerating an Anderson-localized Fermi gas to superdiffusion — Sian Barbosa, Maximilian Kiefer-Emmanouilidis, •Felix Lang, Jennifer Koch, and Artur Widera — Department of Physics and Research Center OPTIMAS, RPTU, 67663 Kaiserslautern, Germany

Disorder can have dramatic impact on the transport properties of quantum systems. Anderson localization, arising from destructive quantum interference of multiple scattering paths suppresses the transport entirely. Processes involving time-dependent random forces such as Fermi acceleration, proposed as a mechanism for high-energy cosmic particles, can expedite particle transport significantly. The competition of these two effects in time-dependent inhomogeneous or disordered potentials can give rise to fascinating dynamics. Experimental observations are paramount, although scarce. Here, I present our experimental study of the dynamics of an ultracold, non-interacting Fermi gas expanding inside a disorder potential with finite spatial and temporal correlations. Depending on the disorder's strength and rate of change, we observe several distinct regimes of tunable anomalous diffusion, ranging from weak localization and subdiffusion to superdiffusion. Especially for strong disorder, where the expansion reveals effects of localization, an intermediate regime is present in which quantum interference appears to counteract acceleration. Our system connects the phenomena of Anderson localization with second-order Fermi acceleration and paves the way toward experimentally investigating Fermi acceleration when entering the regime of quantum transport.

Keywords: Anderson localization; Diffusion; Fermi acceleration; Disorder; Experiment