Radio Frequency Spectroscopy of Trapped Fermi Gases with Population Imbalance

TL;DR

This paper models the RF spectra of population-imbalanced Fermi gases across various temperatures and polarizations, providing insights into the pseudogap phase and questioning the persistence of the pairing gap at high temperatures.

Contribution

It offers a self-consistent theoretical analysis of RF spectra evolution in imbalanced Fermi gases, addressing experimental observations and clarifying the nature of the pseudogap phase.

Findings

RF spectra vary with temperature and polarization

The pseudogap phase can be characterized through RF experiments

The pairing gap likely does not survive up to the degeneracy temperature T_F

Abstract

Motivated by recent experiments, we address, in a fully self consistent fashion, the behavior and evolution of radio frequency (RF) spectra as temperature and polarization are varied in population imbalanced Fermi gases. We discuss a series of scenarios for the experimentally observed zero temperature pseudogap phase and show how present and future RF experiments may help in its elucidation. We conclude that the MIT experiments at the lowest $T$ may well reflect ground state properties, but take issue with their claim that the pairing gap survives up to temperatures of the order of the degeneracy temperature $T_F$ at unitarity.