Spin-orbit coupled Bose-Einstein condensates

TL;DR

This paper explores a new type of Bose-Einstein condensate in spin-orbit coupled bosonic systems, revealing degenerate ground states and potential topological phases, with experimental detection via momentum distribution imaging.

Contribution

It introduces a novel entangled Bose-Einstein condensate arising from spin-orbit coupling and analyzes its properties and degeneracies, expanding understanding of quantum phases in such systems.

Findings

Degenerate ground states with left- and right-moving bosons

Potential for topological phases in symmetric Rashba model

Experimental signatures in momentum distribution patterns

Abstract

We consider a many-body system of pseudo-spin-1/2 bosons with spin-orbit interactions, which couple the momentum and the internal pseudo-spin degree of freedom created by spatially varying laser fields. The corresponding single- particle spectrum is generally anisotropic and contains two degenerate minima at finite momenta. At low temperatures, the many-body system condenses into these minima generating a new type of entangled Bose-Einstein condensate. We show that in the presence of weak density-density interactions the many-body ground state is characterized by a twofold degeneracy. The corresponding many-body wave function describes a condensate of ``left-'' and ``right-moving'' bosons. By fine-tuning the parameters of the laser field, one can obtain a bosonic version of the spin-orbit coupled Rashba model. In this symmetric case, the degeneracy of the ground state is very large, which may lead to phases with nontrivial topological properties. We argue that the predicted new type of Bose-Einstein condensates can be observed experimentally via time-of-flight imaging, which will show characteristic multipeak structures in momentum distribution.