Twin peaks in rf spectra of Fermi gases at unitarity

TL;DR

This paper calculates the radio-frequency spectra of ultracold Fermi gases at unitarity, explaining the observed double-peak structures as effects of inhomogeneity, and matches experimental results without fitting parameters.

Contribution

It demonstrates that the double-peak RF spectra in trapped Fermi gases are due to inhomogeneity, not intrinsic pseudogap effects, aligning theory with experiments.

Findings

Homogeneous gases show single-peak spectra in the normal phase.

Inhomogeneity causes double-peak structures in trapped gases.

Experimental features are reproduced without fitting parameters.

Abstract

We calculate the radio-frequency spectrum of balanced and imbalanced ultracold Fermi gases in the normal phase at unitarity. For the homogeneous case the spectrum of both the majority and minority components always has a single peak even in the pseudogap regime. We furthermore show how the double-peak structures observed in recent experiments arise due to the inhomogeneity of the trapped gas. The main experimental features observed above the critical temperature in the recent experiment of Schunck et al. [Science 316, 867, (2007)] are recovered with no fitting parameters.