Quantum Phases of Two-Component Bosons with Spin-Orbit Coupling in Optical Lattices

TL;DR

This paper explores the rich quantum phase diagram of two-component bosons with spin-orbit coupling in optical lattices, revealing new density and chiral orders, phase transitions, and measurable momentum distributions.

Contribution

It introduces the effects of synthetic spin-orbit coupling on interacting bosons in optical lattices, uncovering novel quantum phases and symmetry-breaking phenomena.

Findings

Discovery of new density- and chiral-ordered phases.

Identification of phase transitions explained by a two-order-parameter model.

Calculation of experimentally measurable momentum distributions for each phase.

Abstract

Ultracold bosons in optical lattices are one of the few systems where bosonic matter is known to exhibit strong correlations. Here we push the frontier of our understanding of interacting bosons in optical lattices by adding synthetic spin-orbit coupling, and show that new kinds of density- and chiral-orders develop. The competition between the optical lattice period and the spin-orbit coupling length -- which can be made comparable in experiments -- along with the spin hybridization induced by a transverse field (i.e., Rabi coupling) and interparticle interactions create a rich variety of quantum phases including uniform, non-uniform and phase-separated superfluids, as well as Mott insulators. The spontaneous symmetry breaking phenomena at the transitions between them are explained by a two-order-parameter Ginzburg-Landau model with multiparticle umklapp processes. Finally, in order to characterize each phase, we calculated their experimentally measurable crystal momentum distributions.