Topological superfluids in two-dimensional Fermi gas with Rashba spin-orbit coupling

TL;DR

This paper uses quantum Monte Carlo simulations to demonstrate topological phase transitions and unconventional pairing in a two-dimensional Fermi gas with Rashba spin-orbit coupling, highlighting deviations from mean-field predictions.

Contribution

It provides the first unbiased, numerically exact evidence of topological superfluids and unconventional pairing in 2D Fermi gases with SOC, beyond mean-field theory assumptions.

Findings

Spin-orbit coupling stabilizes unconventional pairing in weak SOC regime.

Topological phase transitions are identified via spin polarization jumps.

Critical exponents deviate from mean-field theory predictions.

Abstract

The realization of spin-orbit coupling (SOC) in ultracold atoms has triggered an intensive exploring of topological superfluids in the degenerate Fermi gases based on mean-field theory, which has not yet been reported in experiments. Here, we demonstrate the topological phase transitions in the system via the numerically exact quantum Monte Carlo method. Without prior assumptions, our unbiased real-space calculation shows that spin-orbit coupling can stabilize an unconventional pairing in the weak SOC regime, in which the Fulde-Ferrell-Larkin-Ovchinnikov pairing coexists with the Bardeen-Cooper-Schrieffer pairing. Furthermore, we use the jumps in the spin polarization at the time-reversal invariant momenta to qualify the topological phase transition, where we find the critical exponent deviated from the mean-field theory. Our results pave the way for the searching of unconventional pairing and topological superfluids with degenerate Fermi gases.