Many Fermi polarons at nonzero temperature

TL;DR

This paper develops a many-body T-matrix theory to analyze spectral properties of a polarized ultracold Fermi gas with impurities at nonzero temperature, revealing polaron physics and many-polaron effects.

Contribution

It introduces a self-consistent approach to study spectral functions and polaron energies in a finite impurity concentration regime at nonzero temperature.

Findings

Identification of attractive and repulsive polaron energies.

Significance of majority atom renormalization and thermal depletion effects.

Demonstration of polaron physics in a polarized ultracold Fermi mixture.

Abstract

An extremely polarized mixture of an ultracold Fermi gas is expected to reduce to a Fermi polaron system, which consists of a single impurity immersed in the Fermi sea of majority atoms. By developing a many-body T -matrix theory, we investigate spectral properties of the polarized mixture in experimentally relevant regimes in which the system of finite impurity concentration at nonzero temperature is concerned. We explicitly demonstrate presence of polaron physics in the polarized limit and discuss effects of many polarons in an intermediate regime in a self-consistent manner. By analyzing the spectral function at finite impurity concentration, we extract the attractive and repulsive polaron energies. We find that a renormalization of majority atoms via an interaction with minority atoms and a thermal depletion of the impurity chemical potential are of significance to depict the many-polaron regime.