FFLO or Majorana superfluids: The fate of fermionic cold atoms in spin-orbit coupled optical lattices

TL;DR

This paper investigates the competition between FFLO and Majorana superfluid phases in spin-orbit coupled fermionic cold atom systems under Zeeman fields, revealing the conditions under which each phase prevails.

Contribution

It provides a theoretical analysis of the phase diagram of 1D spin-orbit coupled Fermi gases, highlighting the stability regions of FFLO and Majorana superfluids.

Findings

FFLO superfluids can be stabilized in certain parameter regimes.

Majorana superfluids are favored at lower Zeeman fields.

The phase diagram depends critically on spin-orbit coupling strength and Zeeman field.

Abstract

The recent experimental realization of spin-orbit coupling (SOC) for ultra-cold atoms opens a completely new avenue for exploring new quantum matter. In experiments, the SOC is implemented simultaneously with a Zeeman field. Such spin-orbit coupled Fermi gases are predicted to support Majorana fermions with non-Abelian exchange statistics in one dimension (1D). However, as shown in recent theory and experiments for 1D spin-imbalanced Fermi gases, the Zeeman field can lead to the long-sought Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superfluids with non-zero momentum Cooper pairings, in contrast to the zero momentum pairing in Majorana superfluids. Therefore a natural question to ask is which phase, FFLO or Majorana superfluids, will survive in spin-orbit coupled Fermi gases in the presence of a large Zeeman field. In this paper, we address this question by studying the mean field quantum phases of 1D (quasi-1D) spin-orbit coupled fermionic cold atom optical lattices.