Quantum tri-criticality and phase transitions in spin-orbit coupled Bose-Einstein condensates

TL;DR

This paper explores the phase diagram and quantum phase transitions in a spin-orbit coupled Bose-Einstein condensate, identifying a tri-critical point and analyzing various quantum phases and effects of trapping and symmetry breaking.

Contribution

It introduces the concept of a tri-critical point in spin-orbit coupled Bose gases and analyzes the associated quantum phases using mean-field theory.

Findings

Identification of a tri-critical point in the phase diagram

Analysis of momentum distribution and spin polarization across phases

Effects of trapping and symmetry breaking on phase behavior

Abstract

We consider a spin-orbit coupled configuration of spin-1/2 interacting bosons with equal Rashba and Dresselhaus couplings. The phase diagram of the system is discussed with special emphasis to the role of the interaction treated in the mean-field approximation. For a critical value of the density and of the Raman coupling we predict the occurrence of a characteristic tri-critical point separating the spin mixed, the phase separated and the single minimum states of the Bose gas. The corresponding quantum phases are investigated analyzing the momentum distribution, the longitudinal and transverse spin-polarization and the emergence of density fringes. The effect of harmonic trapping as well as the role of the breaking of spin symmetry in the interaction Hamiltonian are also discussed.