Density profiles and collective modes of a Bose-Einstein condensate with light-induced spin-orbit coupling

TL;DR

This paper investigates the phases, density profiles, and collective excitations of a Bose-Einstein condensate with light-induced spin-orbit coupling, revealing unique stability conditions and experimental signatures of the mixed phase.

Contribution

It introduces a mean-field analysis of the phase diagram and density behavior of SOC BECs, highlighting the stability of the mixed phase and its experimental signatures.

Findings

Mixed BEC phase is stable at low light-atom coupling

Density of one spin state increases with radius in the trap

Bogoliubov sound mode vanishes near phase separation boundary

Abstract

The phases of a Bose-Einstein condensate (BEC) with light-induced spin-orbit coupling (SOC) are studied within the mean-field approximation. The mixed BEC phase, in which the system condenses in a superposition of two plane wave states, is found to be stable for sufficiently small light-atom coupling, becoming unstable in a continuous fashion with increasing light-atom coupling. The structure of the phase diagram at fixed chemical potential for bosons with SOC is shown to imply an unusual density dependence for a trapped mixed BEC phase, with the density of one dressed spin state increasing with increasing radius, providing a unique experimental signature of this state. The collective Bogoliubov sound mode is shown to also provide a signature of the mixed BEC state, vanishing as the boundary to the regime of phase separation is approached.