Phase Diagram of a Spin-Orbit Coupled Fermi Gases in a Bilayer Optical Lattice

TL;DR

This paper explores the phase diagram and topological properties of a spin-orbit coupled Fermi gas in a bilayer optical lattice, revealing conditions for topological superfluid phases with Majorana edge states.

Contribution

It provides a mean field analysis of the phase diagram and topological phases, highlighting the conditions under which topological superfluidity occurs in the system.

Findings

First-order phase boundary at half filling

Topologically trivial superfluid at half filling

Topological nontrivial superfluid with Majorana edge states away from half filling

Abstract

We investigate the stability of helical superfluid phase in a spin-orbit coupled Fermi gas loaded in a bilayer optical lattice. The phase diagram of the system is constructed in the mean field framework. We investigate the topological properties of the superfluid phases by a nontrivial application of the Fermi surface topological invariant to our time-reversal invariant system with degeneracies on the Fermi surface. We find that there is a first-order phase boundary in the phase diagram of half filling case and the superfluid phases are all topological trivial. The superfluid phase is topological nontrivial when the filling fraction deviates from the half filling. In the topological nontrivial superfluid phase, a full pairing gap exists in the bulk and gapless helical Majorana edge states exist at the boundary.