Breakdown of the Fermi polaron description near Fermi degeneracy at unitarity

TL;DR

This paper investigates the behavior of attractive Fermi polarons at finite temperature near unitarity, analyzing their spectral properties and the limits of quasiparticle descriptions using many-body theory and virial expansion.

Contribution

It introduces a combined theoretical approach to study Fermi polarons at finite temperature and impurity concentration, focusing on spectral features and quasiparticle validity.

Findings

Calculated rf spectroscopy of polarons at unitarity

Determined temperature range for quasiparticle description

Analyzed polaron energy and lifetime from spectral data

Abstract

We theoretically investigate attractive Fermi polarons in three dimensions at finite temperature and impurity concentration through the many-body T-matrix theory and high-temperature virial expansion. By using the analytically continued impurity Green's function, we calculate the direct rf spectroscopy of attractive polarons in the unitary regime. Taking the peak value of the rf spectroscopy as the polaron energy and the full width half maximum as the polaron lifetime, we determine the temperature range of validity for the quasi-particle description of Fermi polarons in the unitary limit.