Fulde-Ferrell superfluidity in ultracold Fermi gases with Rashba spin-orbit coupling

TL;DR

This paper theoretically demonstrates that in a three-dimensional ultracold Fermi gas with Rashba spin-orbit coupling, the Fulde-Ferrell superfluid state is more stable than the BCS state under an in-plane Zeeman field, and it is observable at attainable temperatures.

Contribution

It provides a mean-field theoretical analysis showing the stability of FF superfluidity over BCS in spin-orbit coupled Fermi gases with Zeeman fields, and predicts experimental observability.

Findings

FF superfluid state is more favorable than BCS state under in-plane Zeeman field.

Predicted FF superfluid is observable at temperatures around 0.2 T_F.

Finite-temperature phase diagram near resonance supports experimental realization.

Abstract

We theoretically investigate the inhomogeneous Fulde-Ferrell (FF) superfluidity in a three dimensional atomic Fermi gas with Rashba spin-orbit coupling near a broad Feshbach resonance. We show that within mean-field theory the FF superfluid state is always more favorable than the standard Bardeen-Cooper-Schrieffer (BCS) superfluid state when an in-plane Zeeman field is applied. We present a qualitative finite-temperature phase diagram near resonance and argue that the predicted FF superfluid is observable with experimentally attainable temperatures (i.e., $T\sim0.2T_{F}$, where $T_{F}$ is the characteristic Fermi degenerate temperature).