Ultracold polarized Fermi gas at intermediate temperatures

TL;DR

This paper investigates the finite-temperature behavior of polarized Fermi gases, revealing stable polarized paired states below the critical temperature and analyzing polarization distribution in traps, highlighting phase separation prior to superfluidity.

Contribution

It demonstrates the existence of stable polarized paired states at finite temperatures and analyzes their behavior in trapped systems using local density approximation.

Findings

Stable polarized paired states exist below the critical temperature.

Polarization increases towards the trap center with temperature.

Phase separation occurs mainly in the fluctuation region before superfluidity.

Abstract

We consider non-zero temperature properties of the polarized two-component Fermi gas. We point out that stable polarized paired states which are more stable than their phase separated counterparts with unpolarized superfluid region can exist below the critical temperature. We also solve the system behavior in a trap using the local density approximation and find gradually increasing polarization in the center of the system as the temperature is increased. However, in the strongly interacting region the central polarization increases most rapidly close to the mean-field critical temperature, which is known to be substantially higher than the critical temperature for superfluidity. This indicates that most of the phase separation occurs in the fluctuation region prior to superfluidity and that the polarization in the actual superfluid is modest.