Radio frequency spectroscopy of a strongly imbalanced Feshbach-resonant Fermi gas

TL;DR

This paper demonstrates that a highly imbalanced Feshbach-resonant Fermi gas remains a strongly-renormalized Fermi liquid, with properties consistent with recent RF spectroscopy experiments, despite being driven into a normal state.

Contribution

It provides a controlled theoretical analysis showing the normal state is a strongly-renormalized Fermi liquid, aligning with recent experimental RF spectra.

Findings

The normal state is a conventional Fermi liquid with strong renormalization.

RF spectra are consistent with a Fermi-liquid description.

The momentum distribution shows the Migdal discontinuity.

Abstract

A sufficiently large species imbalance (polarization) in a two-component Feshbach resonant Fermi gas is known to drive the system into its normal state. We show that the resulting strongly-interacting state is a conventional Fermi liquid, that is, however, strongly renormalized by pairing fluctuations. Using a controlled 1/N expansion, we calculate the properties of this state with a particular emphasis on the atomic spectral function, the momentum distribution functions displaying the Migdal discontinuity, and the radio frequency (RF) spectrum. We discuss the latter in the light of the recent experiments of Schunck et al. (cond-mat/0702066) on such a resonant Fermi gas, and show that the observations are consistent with a conventional, but strongly renormalized Fermi-liquid picture.