Topological spoof plasmon polaritons based on C6-symmetric crystalline metasurfaces

Abstract : We demonstrate topological surface polaritons that propagate on the surface of a two-dimensional (2D) metamaterial made of a subwavelength periodic arrangement of electromagnetic resonators. Such surface modes are obtained at the boundary between 2D domains of distinct topologies, characterized by non-zero spin-Chern invariants, where a spin degree of freedom is induced by relying on six-fold rotational (C6) crystal symmetry combined with time-reversal symmetry. Experiments are conducted in the microwave regime to corroborate the analytical and numerical predictions. Our proposal enables robust subwavelength guiding of electromagnetic waves on a surface along predefined paths.