Josephson effect in an atomic Fulde-Ferrell-Larkin-Ovchinnikov superfluid

TL;DR

This paper theoretically investigates the Josephson effect between two spatially separated atomic superfluids, focusing on how the inhomogeneous FFLO order parameter influences the Josephson current, offering a potential method to detect exotic superfluid phases.

Contribution

It proposes a method to detect FFLO superfluids via Josephson current measurements in a tunable double-well atomic Fermi gas system.

Findings

Maximum Josephson current is proportional to the local order parameter.

Spatial inhomogeneity of FFLO order parameter can be revealed through current measurement.

The study suggests feasible experimental setups for observing these effects.

Abstract

We study theoretically two spatially separate quasi-one-dimensional atomic Fermi gases in a double-well trap. By tuning independently their spin polarizations, a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superfluid or a Bardeen-Cooper-Schrieffer (BCS) superfluid may be formed in each well. We seek the possibility of creating a spatially tunable atomic Josephson junction between two superfluids, which is supposed to be realizable via building a weak link at given positions of the double-well barrier. We show that within mean-field theory the maximum Josephson current is proportional to the order parameter in two wells. Thus, the spatial inhomogeneity of the FFLO order parameter in one well may be directly revealed through the current measurement with the position-tunable link. We anticipate that this type of Josephson measurements can provide a useful evidence for the existence of exotic FFLO superfluids. Possible experimental realizations of the Josephson measurements in atomic Fermi gases are discussed.