Finite temperature effects in trapped Fermi gases with population imbalance

TL;DR

This paper investigates how finite temperature affects trapped imbalanced Fermi gases across the BCS-BEC crossover, revealing phase separation and pseudogap phenomena consistent with recent experiments.

Contribution

It provides a theoretical analysis of finite temperature effects, including polarization behavior and phase separation, in imbalanced Fermi gases during BCS-BEC crossover.

Findings

Superfluid phase transition influences density profiles.

Polarization is excluded from the superfluid core at T ≠ 0.

A normal region carries a significant polarization with strong pair correlations.

Abstract

We study the finite temperature $T$ behavior of trapped Fermi gases as they undergo BCS-Bose Einstein condensation (BEC) crossover, in the presence of a population imbalance. Our results, in qualitative agreement with recent experiments, show how the superfluid phase transition is directly reflected in the particle density profiles. We demonstrate that at $ T \neq 0$ and in the near-BEC and unitary regimes, the polarization is excluded from the superfluid core. Nevertheless a substantial polarization fraction is carried by a normal region of the trap having strong pair correlations, which we associate with noncondensed pairs or the ``pseudogap phase''.