The dynamic behavior of a Fermi gas confined in a deformed trap rotating at low angular velocity is investigated in the framework of hydrodynamic theory. The differences exhibited by a normal gas in the collisional regime and a superfluid are discussed. Special emphasis is given to the collective oscillations excited when the deformation of the rotating trap is suddenly removed or when the rotation is suddenly stopped. The presence of vorticity in the normal phase is shown to give rise to precession and beating phenomena which are absent in the superfluid phase.
Abstract This chapter is devoted to discussing relevant dynamical and superfluid phenomena exhibited by interacting Fermi gases at low temperatures, with special focus on the strongly interacting Fermi gas at unitarity. The chapter discusses the predictions of hydrodynamic theory concerning the propagation of sound, the collective oscillations and the expansion of the gas after release of the trap. The Landau criterion for superfluidity and the behaviour of the dynamic structure factor are discussed. It also provides some considerations on the radiofrequency transitions as a method to observe pair-breaking transitions and to measure the pairing gap. The chapter discusses the behaviour of two-fluid hydrodynamics and the propagation of second sound as a tool to measure the superfluid density of interacting Fermi gases. It finally provides a brief summary of the rotational properties of the superfluid Fermi gas, like the quenching of the moment of inertia and the occurrence of quantized vortices.