Equation of state of a superfluid Fermi gas in the BCS-BEC crossover

TL;DR

This paper develops a theoretical framework for superfluid Fermi gases across the BCS-BEC crossover, incorporating pairing fluctuations, and demonstrates excellent agreement with Quantum Monte Carlo simulations.

Contribution

It introduces a theory that includes pairing fluctuations in the BCS-BEC crossover and accurately reproduces known limits and simulation results.

Findings

Theory recovers Bogoliubov theory in strong coupling limit

Excellent agreement with Quantum Monte Carlo simulations

Accurately describes the equation of state across the crossover

Abstract

We present a theory for a superfluid Fermi gas near the BCS-BEC crossover, including pairing fluctuation contributions to the free energy similar to that considered by Nozieres and Schmitt-Rink for the normal phase. In the strong coupling limit, our theory is able to recover the Bogoliubov theory of a weakly interacting Bose gas with a molecular scattering length very close to the known exact result. We compare our results with recent Quantum Monte Carlo simulations both for the ground state and at finite temperature. Excellent agreement is found for all interaction strengths where simulation results are available.