Ground-state phase diagram and critical temperature of two-component Bose gases with Rashba spin-orbit coupling

TL;DR

This paper maps the ground-state phase diagram of two-component Bose gases with Rashba spin-orbit coupling, revealing phases, phase transitions, and the effects of temperature on Bose condensation.

Contribution

It provides a comprehensive analysis of the phase diagram and critical temperature, highlighting the competition between zero-momentum and spin density wave phases.

Findings

Zero-momentum condensate phase identified

Phase separation occurs near energy degeneracy

Finite temperature induces Bose condensation via ferromagnetic transition

Abstract

Ground-state phase diagram of two-component Bose gases with Rashba spin-orbit coupling is determined via a variational approach. A phase in which the fully polarized condensate occupies zero momentum is identified. This zero-momentum phase competes with the spin density wave phase when interspecies interaction is stronger than intraspecies interaction, and the former one is always the ground state for weak spin-orbit coupling. When the energies of these two phases are close, there is a phase separation between them. At finite temperature, such a zero-momentum condensation can be induced by a ferromagnetic phase transition in normal state. The spontaneous spin polarization removes the degeneracy of quasiparticles' energy minima, and consequently the modified density of state accommodates a Bose condensation to appear below a critical temperature.