Realization of Two-Dimensional Spin-orbit Coupling for Bose-Einstein Condensates

TL;DR

This paper reports the first experimental realization of two-dimensional spin-orbit coupling in a Bose-Einstein condensate of rubidium atoms, enabling exploration of novel quantum phases and topological phenomena.

Contribution

It introduces a minimal optical Raman lattice scheme to achieve 2D SO coupling without phase locking, demonstrating controllable crossover and topological band structures.

Findings

Successful realization of 2D SO coupling in cold atoms.

Observation of nontrivial topological band structures.

Potential to study exotic quantum phases like topological superfluids.

Abstract

Cold atoms with laser-induced spin-orbit (SO) interactions provide intriguing new platforms to explore novel quantum physics beyond natural conditions of solids. Recent experiments demonstrated the one-dimensional (1D) SO coupling for boson and fermion gases. However, realization of 2D SO interaction, a much more important task, remains very challenging. Here we propose and experimentally realize, for the first time, 2D SO coupling and topological band with $^{87}$Rb degenerate gas through a minimal optical Raman lattice scheme, without relying on phase locking or fine tuning of optical potentials. A controllable crossover between 2D and 1D SO couplings is studied, and the SO effects and nontrivial band topology are observed by measuring the atomic cloud distribution and spin texture in the momentum space. Our realization of 2D SO coupling with advantages of small heating and topological stability opens a broad avenue in cold atoms to study exotic quantum phases, including the highly-sought-after topological superfluid phases.