Topological Fulde-Ferrell superfluid in spin-orbit coupled atomic Fermi gases

TL;DR

This paper predicts a new topological inhomogeneous superfluid phase in spin-orbit coupled atomic Fermi gases, characterized by nonzero momentum and Berry phase, which could be experimentally observed using current techniques.

Contribution

It introduces the topological Fulde-Ferrell superfluid phase in one-dimensional atomic Fermi gases with spin-orbit coupling, a novel state not previously characterized.

Findings

Topological Fulde-Ferrell phase exists in a broad parameter space.

The phase can be detected via radio-frequency spectroscopy.

The phase is characterized by a non-trivial Berry phase.

Abstract

We theoretically predict a new topological matter - topological inhomogeneous Fulde-Ferrell superfluid - in one-dimensional atomic Fermi gases with equal Rashba and Dresselhaus spin-orbit coupling near s-wave Feshbach resonances. The realization of such a spin-orbit coupled Fermi system has already been demonstrated recently by using a two-photon Raman process and the extra one-dimensional confinement is easy to achieve using a tight two-dimensional optical lattice. The topological Fulde-Ferrell superfluid phase is characterized by a nonzero center-of-mass momentum and a non-trivial Berry phase. By tuning the Rabi frequency and the detuning of Raman laser beams, we show that such an exotic topological phase occupies a significant part of parameter space and therefore it could be easily observed experimentally, by using, for example, momentum-resolved and spatially resolved radio-frequency spectroscopy.