Adiabatic Phase Diagram of an Ultracold Atomic Fermi Gas with a Feshbach Resonance

TL;DR

This paper maps the adiabatic phase diagram of an ultracold Fermi gas with Feshbach resonance, revealing the condensate composition and molecular conversion efficiency, aiding understanding of BCS-BEC crossover experiments.

Contribution

It extends previous ideal gas models to include resonant interactions using mean-field theory, providing a detailed adiabatic phase diagram and molecular conversion efficiency calculations.

Findings

Condensate fraction includes condensed molecules and Cooper pairs.

Adiabatic phase diagram shows how condensate composition varies with parameters.

Molecular conversion efficiency depends on initial temperature.

Abstract

We determine the adiabatic phase diagram of a resonantly-coupled system of Fermi atoms and Bose molecules confined in the harmonic trap by using the local density approximation. The adiabatic phase diagram shows the fermionic condensate fraction composed of condensed molecules and Cooper pair atoms. The key idea of our work is conservation of entropy through the adiabatic process, extending the study of Williams et al. [Williams et al., New J. Phys. 6, 123 (2004)] for an ideal gas mixture to include the resonant interaction in a mean-field theory. We also calculate the molecular conversion efficiency as a function of initial temperature. Our work helps to understand recent experiments on the BCS-BEC crossover, in terms of the initial temperature measured before a sweep of the magnetic field.