Time-reversal-invariant spin-orbit-coupled bilayer Bose-Einstein Condensates

TL;DR

This paper proposes a realistic scheme to preserve time-reversal symmetry in spin-orbit coupled ultracold Bose gases, revealing symmetry-protected band features and novel interaction-induced phases.

Contribution

It introduces a Hermite-Gaussian-laser scheme to maintain time-reversal symmetry, enabling the study of symmetry-protected quantum states in spin-orbit coupled Bose-Einstein condensates.

Findings

Quantum states form Kramers pairs with protected gap closing.

Interaction induces layer-stripe and uniform phases.

System exhibits spin-layer symmetry and correlations.

Abstract

Time-reversal invariance plays a crucial role for many exotic quantum phases, particularly for topologically nontrivial states, in spin-orbit coupled electronic systems. Recently realized spin-orbit coupled cold-atom systems, however, lack the time-reversal symmetry due to the inevitable presence of an effective transverse Zeeman field. We address this issue by analyzing a realistic scheme to preserve time-reversal symmetry in spin-orbit coupled ultracold atoms, with the use of Hermite-Gaussian-laser induced Raman transitions that preserve spin-layer time-reversal symmetry. We find that the system's quantum states form Kramers pairs, resulting in symmetry-protected gap closing of the lowest two bands at arbitrarily large Raman coupling. We also show that Bose gases in this setup exhibit interaction-induced layer-stripe and uniform phases as well as intriguing spin-layer symmetry and spin-layer correlation.