Pairing effects in the normal phase of a two-dimensional Fermi gas

TL;DR

This paper investigates the nature of the pairing gap in a 2D Fermi gas, distinguishing between pseudogap and molecular states using a t-matrix approach, and relates 2D and 3D pseudogap phenomena across the BCS-BEC crossover.

Contribution

It provides a theoretical framework that reproduces experimental data and clarifies the boundary between pseudogap and molecular regimes in 2D Fermi gases.

Findings

Reproduces experimental pairing gap data in 2D Fermi gases.

Defines the boundary between pseudogap and molecular regimes.

Shows a universal relation of pseudogap phenomena across dimensions.

Abstract

In a recent experiment [M. Feld et al., Nature 480, 75 (2011); B. Froehlich et al., Phys. Rev. Lett. 109,130403 (2012)], a pairing gap was detected in a two-dimensional (2D) Fermi gas with attractive interaction at temperatures where superfluidity does not occur. The question remains open as to whether this gap is a pseudogap phenomenon or is due to a molecular state. In this paper, by using a t-matrix approach, we reproduce quite well the experimental data for a 2D Fermi gas, and set the boundary between the pseudogap and molecular regimes. We also show that pseudogap phenomena occurring in 2D and 3D can be related through a variable spanning the BCS-BEC crossover in a universal way.