Radio Frequency Spectroscopy of a Strongly Imbalanced Feshbach-Resonant Fermi Gas

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. (Science 316, 867 (2007)) on such a resonant Fermi gas, and show that the observations are consistent with a conventional, but strongly renormalized Fermi-liquid picture.