Finite temperature phase diagram of trapped Fermi gases with population imbalance

TL;DR

This paper maps the finite temperature phase diagram of trapped imbalanced Fermi gases across a Feshbach resonance, highlighting the limited stability and observability of the LOFF state.

Contribution

It provides a detailed phase diagram considering the LOFF state and demonstrates its stability conditions in trapped Fermi gases.

Findings

LOFF state stable only on the BCS side

LOFF state exists at low temperatures and in small trap regions

Direct observation of LOFF state is challenging

Abstract

We consider a trapped Fermi gas with population imbalance at finite temperatures and map out the detailed phase diagram across a wide Feshbach resonance. We take the Larkin-Ovchinnikov-Fulde-Ferrel (LOFF) state into consideration and minimize the thermodynamical potential to ensure stability. Under the local density approximation, we conclude that a stable LOFF state is present only on the BCS side of the Feshbach resonance, but not on the BEC side or at unitarity. Furthermore, even on the BCS side, a LOFF state is restricted at low temperatures and in a small region of the trap, which makes a direct observation of LOFF state a challenging task.