Pair excitations and parameters of state of imbalanced Fermi gases at finite temperatures

TL;DR

This paper analytically derives the spectra of low-lying pair excitations in imbalanced superfluid Fermi gases at finite temperatures, providing insights into thermodynamic parameters and sound velocities, with results aligning well with Monte Carlo data and experiments.

Contribution

It introduces an analytical approach to calculate pair excitation spectra in imbalanced Fermi gases at finite temperatures, including Gaussian fluctuations.

Findings

Spectra agree with Monte Carlo data.

Calculated thermodynamic parameters match experimental results.

First and second sound velocities are derived from the spectra.

Abstract

The spectra of low-lying pair excitations for an imbalanced two-component superfluid Fermi gas are analytically derived within the path-integral formalism taking into account Gaussian fluctuations about the saddle point. The spectra are obtained for nonzero temperatures, both with and without imbalance, and for arbitrary interaction strength. On the basis of the pair excitation spectrum, we have calculated the thermodynamic parameters of state of cold fermions and the first and second sound velocities. The parameters of pair excitations show a remarkable agreement with the Monte Carlo data and with experiment.