DC Josephson Effect with Fermi gases in the Bose-Einstein regime

TL;DR

This paper models the DC Josephson effect in ultracold Fermi gases within the BEC regime using a nonlinear Schrödinger equation, aligning well with Bogoliubov-de Gennes results and highlighting significant beyond mean-field effects.

Contribution

It introduces a superfluid NLSE that accurately describes the Josephson effect in the BEC regime, extending the Gross-Pitaevskii framework with the correct equation of state.

Findings

Superfluid NLSE matches Bogoliubov-de Gennes calculations in the BEC regime.

Predicted Josephson current exhibits notable beyond mean-field effects.

Model reliable up to large positive scattering lengths.

Abstract

We show that the DC Josephson effect with ultracold fermionic gases in the BEC regime of composite molecules can be described by a nonlinear Schrodinger equation (NLSE). By comparing our results with Bogoliubov-de Gennes calculations [Phys. Rev. Lett. 99, 040401 (2007)] we find that our superfluid NLSE, which generalizes the Gross-Pitaevskii equation taking into account the correct equation of state, is reliable in the BEC regime of the BCS-BEC crossover up to the limit of very large (positive) scattering length. We also predict that the Josephson current displays relevant beyond mean-field effects.