Spin-orbit coupling, the interaction between spin and motional degrees of freedom of a particle, has played a crucial role in many physics subfields ranging from atomic fine structures to topological solid state materials. In this context, the recent experimental realization of spin-orbit coupling in ultracold atomic gases provides a powerful tool for exploring novel quantum matter because of the high controllability and disorder-free of ultracold atoms. Previous studies have mainly focused on spin-vectors, while high-order spin-tensors naturally exist in a high-spin (larger or equal to 1) system. In this talk, I will discuss the realization of spin-tensor-momentum coupling in ultracold atomic gases as well as the resulting exotic quantum matters. In particular, I will show the emergence of superfluid stripe phases with supersolid-like properties and topological triply-degenerate fermions, new quasiparticles that have no analog in quantum field theory. Finally, I will show th at topological triply-degenerate points could also be realized with photons in non-Hermitian hyperbolic metamaterials.

Relevant publications:

- X.-W. Luo, K. Sun, C. Zhang, Spin-tensor--momentum-coupled Bose-Einstein condensates, Phys. Rev. Lett. 119, 193001 (2017).
- H. Hu, J. Hou, F. Zhang, C. Zhang, Topological Triply-Degenerate Points Induced by Spin-Tensor-Momentum Couplings, Phys. Rev. Lett. 120, 240401 (2018).
- H. Hu, C. Zhang, Spin-1 Topological Monopoles in Parameter Space of Ultracold Atoms, Phys. Rev. A 98, 013627 (2018).
- Tunable spin superstripe phase with a long period and high visibility, X.-W. Luo, C. Zhang, arXiv:1806.10568.
- J. Hou, Z. Li, X.-W. Luo, Q. Gu, C. Zhang, Topological bands and triply-degenerate points in non-Hermitian hyperbolic metamaterials, arXiv:1808.06972.