Temperature and final state effects in radio frequency spectroscopy experiments on atomic Fermi gases

TL;DR

This paper systematically analyzes RF spectra of atomic Fermi gases at finite temperatures, revealing the continuum from thermally excited quasiparticles and explaining recent experimental observations with predictions on temperature effects.

Contribution

It provides a comprehensive characterization of RF spectra including final state interactions and introduces methods to detect thermally excited quasiparticle continua.

Findings

Detection of the $ u < 0$ continuum from thermally excited quasiparticles

Exact satisfaction of sum rules at all temperatures

Semi-quantitative explanation of recent RF experiments

Abstract

We present a systematic characterization of the radio frequency (RF) spectra of homogeneous, paired atomic Fermi gases at finite temperatures, $T$, in the presence of final state interactions. The spectra, consisting of possible bound states and positive as well as negative detuning ($\nu$) continua, satisfy exactly the zeroth- and first-moment sum rules at all $T$. We show how to detect the $\nu < 0$ continuum arising from thermally excited quasiparticles, which has not yet been seen experimentally. We explain semi-quantitatively recent RF experiments on "bound-bound" transitions and, thereby, predict the associated effects of varying temperature.