Probing quantum many-body dynamics in a uniform Fermi gas

Ultracold fermions in optical box traps are a fascinating platform for studying nonequilibrium many-body dynamics in highly controllable settings [1]. In this talk, I will present three such studies: (i) Using impurities with two internal states immersed in a Fermi sea, we realize radio-frequency–dressed Fermi polarons with interactions tunable by an rf field. We observe many-body–renormalized Rabi oscillations and characterize the interaction-dependent frequency shift, renormalized Rabi frequency and damping rate, which we connect to properties of the rf-dressed polaron [2]. (ii) By spatially driving a uniform Fermi gas, we determine the density–density response across interaction regimes, directly measuring the celebrated Lindhard response at weak coupling and the emergence of the collective first-sound mode toward stronger interactions. We also extract a damping rate characteristic of a crossover Fermi liquid [3]. (iii) By tuning the power and pulse duration of an rf, we map the generic dynamical response of a strongly interacting Fermi gas coupled to a probing field, from the universal early-time quadratic regime to the onset and breakdown of Fermi’s Golden Rule, and into coherent many-body Rabi dynamics [4].