Quasi-condensation in two-dimensional Fermi gases

TL;DR

This paper investigates quasi-condensation in two-dimensional Fermi gases, revealing its similarities to BKT behavior, characterized by a zero momentum peak and a well-defined crossover temperature, aligning with recent experimental findings.

Contribution

It combines experimental protocols with simple theory to elucidate the physical nature of quasi-condensation and its relation to BKT physics in 2D Fermi gases.

Findings

Quasi-condensation exhibits BKT-like features including a zero momentum peak.

Disappearance of quasi-condensation occurs at a specific crossover temperature.

Phase diagram and pair distribution match recent experimental observations.

Abstract

In this paper we follow the analysis and protocols of recent experiments, combined with simple theory, to arrive at a physical understanding of quasi-condensation in two dimensional Fermi gases. We find that quasi-condensation mirrors Berezinskii-Kosterlitz-Thouless behavior in many ways, including the emergence of a strong zero momentum peak in the pair momentum distribution. Importantly, the disappearance of this quasi-condensate occurs at a reasonably well defined crossover temperature. The resulting phase diagram, pair momentum distribution, and algebraic power law decay are compatible with recent experiments throughout the continuum from BEC to BCS.