Two-dimensional spin-imbalanced Fermi gases at non-zero temperature: Phase separation of a non-condensate

TL;DR

This paper investigates phase separation in two-dimensional spin-imbalanced Fermi gases at non-zero temperatures, revealing the role of non-condensed pairs and predicting features of the quasi-condensate phase.

Contribution

It provides the first detailed analysis of phase separation involving non-condensed pairs in 2D Fermi gases and offers predictions for the onset of quasi-condensation.

Findings

Reasonable agreement with experimental density profiles at moderate temperatures

Phase separation linked to non-condensed fermion pairs in 2D

Distinctive features in profiles indicating quasi-condensation onset

Abstract

We study a trapped two-dimensional spin-imbalanced Fermi gas over a range of temperatures. In the moderate temperature regime, associated with current experiments, we find reasonable semi-quantitative agreement with the measured density profiles as functions of varying spin imbalance and interaction strength. Our calculations show that, in contrast to the three-dimensional case, the phase separation which appears as a spin balanced core, can be associated with non-condensed fermion pairs. We present predictions at lower temperatures where a quasi-condensate will first appear, based on the pair momentum distribution and following the protocols of Jochim and collaborators. While these profiles also indicate phase separation, they exhibit distinctive features which may aid in identifying the condensation regime.