Route to Observable Fulde-Ferrell-Larkin-Ovchinnikov Phases in 3D Spin-Orbit Coupled Degenerate Fermi Gases

TL;DR

This paper proposes that FFLO phases can be observed in 3D spin-orbit coupled Fermi gases with in-plane Zeeman field, providing a new platform to explore elusive FFLO states under realistic experimental conditions.

Contribution

It demonstrates the potential realization of FFLO phases in 3D Fermi gases with spin-orbit coupling, expanding the experimental avenues beyond 2D superconductors.

Findings

FFLO phases can exist in a large parameter space in 3D Fermi gases.

The FFLO phase is stable at experimentally achievable temperatures.

The phase arises from Fermi surface asymmetry and superfluid order interplay.

Abstract

The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase was first predicted in 2D superconductors about 50 years ago, but so far unambiguous experimental evidences are still lacked. The recently experimentally realized spin-imbalanced Fermi gases may potentially unveil this elusive state, but require very stringent experimental conditions. In this Letter, we show that FFLO phases may be observed even in a 3D degenerate Fermi gas with spin-orbit coupling and in-plane Zeeman field. The FFLO phase is driven by the interplay between asymmetry of Fermi surface and superfluid order, instead of the interplay between magnetic and superconducting order in solid materials. The predicted FFLO phase exists in a giant parameter region, possesses a stable long-range superfluid order due to the 3D geometry, and can be observed with experimentally already achieved temperature ($T\sim 0.05E_{F}$), thus opens a new fascinating avenue for exploring FFLO physics.