Zero Sound in Dipolar Fermi Gases

TL;DR

This paper investigates zero sound propagation in dipolar Fermi gases, revealing directional dependence and instability thresholds related to dipole moments, with implications for understanding collective excitations in quantum gases.

Contribution

It provides the first analysis of anisotropic zero sound modes and identifies conditions for stability and collapse in dipolar Fermi gases.

Findings

Undamped zero sound exists only within specific angular ranges.

A critical dipole moment leads to local collapse perpendicular to polarization.

The study maps stability conditions for dipolar Fermi gases.

Abstract

We study the propagation of sound in a homogeneous dipolar gas at zero temperature, known as zero sound. We find that undamped sound propagation is possible only in a range of solid angles around the direction of polarization of the dipoles. Above a critical dipole moment, we find an unstable mode, by which the gas collapses locally perpendicular to the dipoles' direction.