Evolution of the Pseudogap in a polarized Fermi gas

TL;DR

This paper investigates how the pseudogap in a polarized Fermi gas evolves across the BCS-BEC crossover, revealing that polarization causes the pseudogap to become more diffuse and shift away from the Fermi level.

Contribution

It provides a detailed analysis of the spectral density and pseudogap behavior in polarized Fermi gases using a T-matrix approximation, highlighting the impact of polarization.

Findings

Pseudogap becomes more diffuse with increased polarization.

The pseudogap shifts away from the Fermi level as polarization increases.

Non-condensed pairs significantly influence the spectral density.

Abstract

We calculate the single particle spectral density of a normal (non-superfluid) two component gas of fermions in the BCS-BEC crossover within a T-matrix approximation. We review how non-condensed pairs lead to a spectral density reminiscent of the ordered state, and explore how a gap-like feature in the spectrum evolves as one changes the polarization of the gas. As the gas is polarized we find that this pseudogap becomes more diffuse and moves away from the Fermi level, reflecting the fact that fewer pairs are present but that they still play an important role in the excitations.