Sian Barbosa, Maximilian Kiefer-Emmanouilidis, Felix Lang, Jennifer Koch, Artur Widera: Â
🔓 arXiv:2311.08224 (2023)
Disorder can have dramatic impact on the transport properties of quantum systems. On the one hand, Anderson localization, arising from destructive quantum interference of multiple-scattering paths, can halt transport entirely. On the other hand, 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 interesting dynamics but experimental observations are scarce. Here, we experimentally study 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 shows 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 to experimentally investigating Fermi acceleration when entering the regime of quantum transport.