Spin-orbit coupling driven superfluid states in optical lattices at zero and finite temperatures

TL;DR

This paper explores how spin-orbit coupling influences superfluid phases in a 2D Bose-Hubbard model, revealing novel finite-momentum superfluids and phase transitions affected by temperature and interaction strengths.

Contribution

It introduces the effects of Rashba spin-orbit coupling on superfluid phases and phase transitions in the Bose-Hubbard model at zero and finite temperatures.

Findings

Spin-orbit coupling induces finite-momentum superfluid phases.

Thermal fluctuations suppress phase-twisted superfluidity.

Transitions between superfluid, stripe, and ferromagnetic phases are characterized.

Abstract

We investigate the quantum phase transitions of a two-dimensional Bose-Hubbard model in the presence of a Rashba spin-orbit coupling with and without thermal fluctuations. The interplay of single-particle hopping, strength of spin-orbit coupling, and interspin interaction leads to superfluid phases with distinct properties. With interspin interactions weaker than intraspin interactions, the spin-orbit coupling induces two finite-momentum superfluid phases. One of them is a phase-twisted superfluid that exists at low hopping strengths and reduces the domain of insulating phases. At comparatively higher hopping strengths, there is a transition from the phase-twisted to a finite momenta stripe superfluid. With interspin interactions stronger than the intraspin interactions, the system exhibits phase-twisted to ferromagnetic phase transition. At finite temperatures, the thermal fluctuations destroy the phase-twisted superfluidity and lead to a wide region of normal-fluid states. These findings can be observed in recent quantum gas experiments with spin-orbit coupling in optical lattices.