Intermediate temperature superfluidity in an atomic Fermi gas with population imbalance

TL;DR

This paper develops a finite temperature theoretical framework for population-imbalanced Fermi gas superfluidity, calculating phase diagrams and revealing an intermediate temperature superfluid phase at unitarity.

Contribution

It introduces a comprehensive finite temperature theory for imbalanced Fermi gases, including phase diagrams and the identification of an intermediate temperature superfluid state.

Findings

Finite temperature stabilizes superfluidity.

Two solutions for the critical temperature $T_c$ are found.

An intermediate temperature superfluid state exists at unitarity.

Abstract

We derive the underlying finite temperature theory which describes Fermi gas superfluidity with population imbalance in a homogeneous system. We compute the pair formation temperature and superfluid transition temperature $T_c$ and superfluid density in a manner consistent with the standard ground state equations, and thereby present a complete phase diagram. Finite temperature stabilizes superfluidity, as manifested by two solutions for $T_c$, or by low $T$ instabilities. At unitarity the polarized state is an ``intermediate temperature superfluid".