DC and AC Josephson effects with superfluid Fermi atoms across a Feshbach resonance

TL;DR

This paper demonstrates that a nonlinear Schrödinger equation effectively describes both DC and AC Josephson effects in superfluid Fermi gases across the BCS-BEC crossover at zero temperature, with applicability on both sides of the crossover.

Contribution

It introduces a nonlinear Schrödinger equation framework for superfluid Fermi gases that aligns with mean-field calculations on the BEC side and extends to the BCS side with a phenomenological tunneling parameter.

Findings

NLSE accurately models Josephson effects on the BEC side

NLSE remains reliable up to the unitarity limit

Applicable to weakly-linked superfluids on the BCS side

Abstract

We show that both DC and AC Josephson effects with superfluid Fermi atoms in the BCS-BEC crossover can be described at zero temperature by a nonlinear Schrodinger equation (NLSE). By comparing our NLSE with mean-field extended BCS calculations, we find that the NLSE is reliable in the BEC side of the crossover up to the unitarity limit. The NLSE can be used for weakly-linked atomic superfluids also in the BCS side of the crossover by taking the tunneling energy as a phenomenological parameter.