Spin-orbit coupling (SOC) plays a significant role in many fundamental topological phenomena in solids. Ultracold atoms provide a highly controllable and pristine platform to explore SOC. We experimentally realised a fully optical SOC by Raman coupling nuclear spin states of ytterbium atoms. Furthermore, an optical lattice dressed by SOC, termed the Raman lattice, can host novel topological states such as symmetry-protected topological phases and nodal-line semimetals.

References:

[1] B. Song, C. He, S. Zhang, E. Hajiyev, W. Huang, X.-J. Liu, G.-B. Jo, Spin-orbit coupled two-electron Fermi gases of ytterbium atoms, Physical Review A 94, 061604(R) (2016)

[2] B. Song, L. Zhang, C. He, T. F. J. Poon, E. Hajiyev, S. Zhang, X.-J. Liu and G.-B. Jo, Observation of symmetry-protected topological band with ultracold fermions, Science Advances 4, eaao4748 (2018)

[3] B. Song, C. He, S. Niu, L. Zhang, Z. Ren, X.-J. Liu and G.-B. Jo, Observation of nodal-line semimetal with ultracold fermions in an optical lattice, Nature Physics 15, 911 (2019)