Larkin-Ovchinikov superfluidity in time-reversal symmetric bilayer Fermi gases

TL;DR

This paper predicts a novel realization of the Larkin-Ovchinnikov superfluid phase in a time-reversal and spatial-inversion symmetric bilayer Fermi gas, leveraging laser-assisted tunneling and effective p-wave pairing, without requiring spin imbalance.

Contribution

It introduces a new method to realize LO superfluidity in symmetric bilayer Fermi gases through laser-assisted tunneling and pseudospin interactions, avoiding the need for spin imbalance.

Findings

LO state can be realized in symmetric bilayer Fermi gases.

Effective p-wave pairing arises from s-wave interactions via pseudospin coupling.

Spontaneous density modulation of pairing order is predicted in broad parameter regimes.

Abstract

Larkin-Ovchinnikov (LO) state which combines the superfluidity and spatial periodicity of pairing order parameter and exhibits the supersolid properties has been attracting intense attention in both condensed matter physics and ultracold atoms. Conventionally, realization of LO state from an intrinsic s-wave interacting system necessitates to break the time-reversal (TR) and sometimes spatial-inversion (SI) symmetries. Here we report a novel prediction that the LO state can be realized in a TR and SI symmetric system representing a bilayer Fermi gas subjected to a laserassisted interlayer tunneling. We show that the intralayer s-wave atomic interaction acts effectively like a p-wave interaction in the pseudospin space. This provides distinctive pairing effects in the present system with pseudspin spin-orbit coupling, and leads to a spontaneous density-modulation of the pairing order predicted in a very broad parameter regime. Unlike the conventional schemes, our results do not rely on the spin imbalance or external Zeeman fields, showing a highly feasible way to observe the long-sought-after LO superfluid phase using the laser-assisted bilayer Fermi gases.