Collective modes in the anisotropic unitary Fermi gas and the inclusion of a backflow term

TL;DR

This paper investigates collective excitations in an anisotropic unitary Fermi gas using extended superfluid hydrodynamics, highlighting the impact of a backflow term on sound propagation and phonon damping.

Contribution

It introduces the inclusion of a backflow term in the superfluid Lagrangian and analyzes its effects on collective modes and damping mechanisms.

Findings

Backflow term modifies sound wave behavior.

Backflow influences Beliaev damping of phonons.

Anisotropic confinement affects collective mode frequencies.

Abstract

We study the collective modes of the confined unitary Fermi gas under anisotropic harmonic confinement as a function of the number of atoms. We use the equations of extended superfluid hydrodynamics, which take into account a dispersive von Weizsacker-like term in the equaton of state. We also discuss the inclusion of a backflow term in the extended superfluid Lagrangian and the effects of this anomalous term on sound waves and Beliaev damping of phonons.