Floquet engineering of a uniform potential for a strongly-interacting Fermi gas

Ultracold atoms are a powerful resource for quantum technologies thanks to their unparalleled controllability. Floquet engineering is a powerful approach to implement novel effective Hamiltonians by employing periodic modulation. Such driving of a generic interacting many-body system eventually leads to heating. Still, at intermediate times, which are exponentially long with the driving frequency, the heating rate may be extremely low. During this time, the system assumes a prethemalized meta-stable state. Here we report on the first application of Floquet engineering with a strongly interacting Fermi gas in free space. Our engineered Hamiltonian is a flat potential for a mixture of two-spin states. It is created by an external magnetic field that counteracts most of the gravitational potential and concurrently the application of a rf field that induces a rapid spin rotation. We observe no heating on experimentally relevant timescales, when the driving frequency is high enough. In this regime, physical observables behave similar to those of a stationary gas at thermal equilibrium. In particular, we measure the pair-condensation fraction of a fermionic superfluid at unitarity and the contact parameter in the BEC-BCS crossover. The condensate fraction exhibits a non-monotonic dependence on the drive frequency and reaches a value higher than its value without driving. The contact parameter agrees with recent theories and calculations for a uniform stationary gas. Finally, we discuss possible routes to implementation of artificial gauge fields using Floquet engineering with a Fermi gases in the continuum.