Equilibrium and dynamics of a trapped superfluid Fermi gas with unequal masses

TL;DR

This paper analyzes the equilibrium and collective dynamics of a trapped superfluid Fermi gas with unequal masses, providing stability conditions and behavior predictions near Feshbach resonances.

Contribution

It derives stability conditions and collective oscillation frequencies for mass-imbalanced superfluid Fermi gases using hydrodynamic theory.

Findings

Stability conditions depend on mass ratio and trap frequencies.

Predicted collective oscillation modes for specific mixtures.

Behavior of the gas after one component's trap is turned off.

Abstract

Interacting Fermi gases with equal populations but unequal masses are investigated at zero temperature using local density approximation and the hydrodynamic theory of superfluids in the presence of harmonic trapping. We derive the conditions of energetic stability of the superfluid configuration with respect to phase separation and the frequencies of the collective oscillations in terms of the mass ratio and the trapping frequencies of the two components. We discuss the behavior of the gas after the trapping potential of a single component is switched off and show that, near a Feshbach resonance, the released component can still remain trapped due to many-body interaction effects. Explicit predictions are presented for a mixture of $^6$Li and $^{40}$K with resonant interaction.