Collective modes of a two-dimensional spin-1/2 Fermi gas in a harmonic trap

TL;DR

This paper analytically investigates the collective modes of a two-dimensional spin-1/ick Fermi gas in a harmonic trap, revealing how strong coupling and trap anisotropy influence damping and frequency, aligning well with experimental observations.

Contribution

It provides analytical expressions for collective mode frequencies and damping, highlighting the impact of pairing correlations and trap anisotropy in strongly coupled 2D Fermi gases.

Findings

Pairing correlations increase collision rates beyond classical predictions.

Trap anisotropy causes damping of breathing modes consistent with experiments.

The crossover from collisionless to hydrodynamic behavior is characterized for the quadruple mode.

Abstract

We derive analytical expressions for the frequency and damping of the lowest collective modes of a two-dimensional Fermi gas using kinetic theory. For strong coupling, we furthermore show that pairing correlations overcompensate the effects of Pauli blocking on the collision rate for a large range of temperatures, resulting in a rate which is larger than that of a classical gas. Our results agree well with experimental data, and they recover the observed cross-over from collisionless to hydrodynamic behaviour with increasing coupling for the quadruple mode. Finally, we show that a trap anisotropy within the experimental bounds results in a damping of the breathing mode which is comparable to what is observed, even for a scale invariant system.