Artificial spin-orbit coupling in ultra-cold Fermi superfluids

TL;DR

This paper develops a theoretical framework for ultra-cold Fermi superfluids with spin-orbit coupling, revealing the emergence of various topological superfluid phases with complex pairing symmetries and gapless excitations.

Contribution

It introduces a comprehensive theory showing how spin-orbit coupling and Zeeman fields induce topological superfluid phases with higher angular momentum components.

Findings

Multiple topological superfluid phases identified

Gapped s-wave superfluids can develop p-, d-, f-wave components

Presence of multi-critical points separating phases

Abstract

We develop a theory for interacting fermions in the presence of spin-orbit coupling and Zeeman fields, and show that many new superfluids phases, which are topological in nature, emerge. Depending on values of spin-orbit coupling, Zeeman fields, and interactions, initially gapped s-wave superfluids acquire p-wave, d-wave, f-wave and higher angular momentum components, which produce zeros in the excitation spectrum, rendering the superfluid gapless. Several multi-critical points, which separate topological superfluid phases from normal or non-uniform, are accessible depending on spin-orbit coupling, Zeeman fields or interactions, setting the stage for the study of tunable topological superfluids.