Stabilizing an Ultracold Fermi Gas against Fermi Acceleration to Superdiffusion through Localization

Anderson localization, i.e., destructive quantum interference of multiple-scattering paths, halts transport entirely. Contrarily, time-dependent random forces expedite transport via Fermi acceleration, proposed as a mechanism for high-energy cosmic rays. Their competition creates interesting dynamics, but experimental observations are scarce. Here, we experimentally study the expansion of an ultracold Fermi gas inside time-dependent disorder and observe distinct regimes from sub- to superdiffusion. Unexpectedly, quantum interference counteracts acceleration in strong disorder before a transition to a diffusive state occurs in the driven system. Our system enables the investigation of Fermi acceleration in the quantum-transport regime.