Expansion of a Fermi Cloud in the BCS-BEC Crossover

TL;DR

This paper investigates the free expansion dynamics of a two-component Fermi gas across the BCS-BEC crossover using density-functional theory, comparing theoretical predictions with experimental data to understand the effects of interaction regimes.

Contribution

It introduces a parameter-free density-functional approach with two equations of state to model Fermi gas expansion, highlighting the better agreement of mean-field theory with experiments.

Findings

Mean-field theory aligns more closely with experimental data.

Both models predict aspect ratio dependence on expansion time and scattering length.

The study provides insights into the expansion behavior across the BCS-BEC crossover.

Abstract

We study the free expansion of a dilute two-component Fermi gas with attractive interspecies interaction in the BCS-BEC crossover. We apply a time-dependent parameter-free density-functional theory by using two choices of the equation of state: an analytic formula based on Monte Carlo data and the mean-field equation of state resulting from the extended BCS equations. The calculated axial and transverse radii and the aspect ratio of the expanding cloud are compared to experimental data on vapors of ^6Li atoms. Remarkably, the mean-field theory shows a better agreement with the experiments than the theory based on the Monte Carlo equation of state. Both theories predict a measurable dependence of the aspect ratio on expansion time and on scattering length.