Expansion of an interacting Fermi gas

TL;DR

This paper investigates how a dilute ultracold Fermi gas expands after being released from an anisotropic trap, revealing differences in expansion behavior between normal and superfluid phases, which can serve as experimental signatures.

Contribution

It provides theoretical predictions on the expansion dynamics of interacting Fermi gases, highlighting the contrasting behaviors in normal and superfluid phases, including aspect ratio inversion phenomena.

Findings

Superfluid phase shows inversion of cloud deformation during expansion.

Normal phase does not exhibit aspect ratio inversion if interactions are attractive.

Expansion dynamics can distinguish between normal and superfluid states.

Abstract

We study the expansion of a dilute ultracold sample of fermions initially trapped in a anisotropic harmonic trap. The expansion of the cloud provides valuable information about the state of the system and the role of interactions. In particular the time evolution of the deformation of the expanding cloud behaves quite differently depending on whether the system is in the normal or in the superfluid phase. For the superfluid phase, we predict an inversion of the deformation of the sample, similarly to what happens with Bose-Einstein condensates. Viceversa, in the normal phase, the inversion of the aspect ratio is never achieved, if the mean field interaction is attractive and collisions are negligible.