Response function of strongly interacting Fermi gas in a virial expansion

TL;DR

This paper investigates the dynamic response functions of a strongly interacting Fermi gas using a second-order virial expansion, revealing the atomic to molecular transition during BCS-BEC crossover and aligning with experimental observations.

Contribution

It introduces a virial expansion approach to accurately analyze the many-body response of strongly interacting Fermi gases at low density and high temperature.

Findings

Density response transitions from atomic to molecular with increasing interaction strength

Qualitative agreement with Bragg spectroscopy experimental results

Virial response provides an exact benchmark at low density and high temperature

Abstract

The dynamic response functions of strongly interacting fermion gas in homogeneous space are investigated in a virial expansion to second order. The density response function exhibits transition from atomic to molecular response, as the interaction strength increases and the system undergoes BCS-BEC crossover. The qualitative features of density and spin response agree with measurements from the Bragg spectroscopy experiments. The virial response is exact at low density and high temperature, therefore providing a benchmark for many-body response.