Momentum distribution and condensate fraction of a Fermi gas in the BCS-BEC crossover

TL;DR

This paper uses diffusion Monte Carlo simulations to analyze the momentum distribution and condensate fraction of an interacting Fermi gas across the BCS-BEC crossover at zero temperature, providing detailed insights into pairing and superfluidity.

Contribution

It presents the first comprehensive calculation of the momentum distribution and condensate fraction of a Fermi gas across the BCS-BEC crossover using diffusion Monte Carlo methods.

Findings

Momentum distribution varies with interaction strength.

Off-diagonal long-range order is confirmed.

Condensate fraction is quantified at unitarity and beyond.

Abstract

By using the diffusion Monte Carlo method we calculate the one- and two-body density matrix of an interacting Fermi gas at T=0 in the BCS-BEC crossover. Results for the momentum distribution of the atoms, as obtained from the Fourier transform of the one-body density matrix, are reported as a function of the interaction strength. Off-diagonal long-range order in the system is investigated through the asymptotic behavior of the two-body density matrix. The condensate fraction of fermionic pairs is calculated in the unitary limit and on both sides of the BCS-BEC crossover.