Superradiant Phase Transition of Fermi Gases in a Cavity across a Feshbach Resonance

TL;DR

This paper investigates how the superradiant phase transition in a two-component Fermi gas within a cavity varies across a Feshbach resonance, revealing a crossover from fermionic to bosonic behavior and identifying conditions for maximal superradiance.

Contribution

It demonstrates the continuous crossover of superradiant phase transition characteristics from fermionic to bosonic regimes across the Feshbach resonance in a Fermi gas.

Findings

Superradiance is enhanced in the unitary regime at low densities.

Superradiance peaks near Fermi surface nesting in the BCS regime.

Maximum superradiance occurs in the BEC regime at high densities.

Abstract

In this letter we consider the superradiant phase transition of a two-component Fermi gas in a cavity across a Feshbach resonance. It is known that quantum statistics plays a crucial role for the superradiant phase transition in atomic gases; in contrast to bosons, in a Fermi gas this transition exhibits strong density dependence. We show that across a Feshbach resonance, while the two-component Fermi gas passes through the BEC-BCS crossover, the superradiant phase transition undergoes a corresponding crossover from a fermionic behavior on the weakly interacting BCS side, to a bosonic behavior on the molecular BEC side. This intricate statistics crossover makes the superradiance maximally enhanced either in the unitary regime for low densities, in the BCS regime for moderate densities close to Fermi surface nesting, or in the BEC regime for high densities.