Plasmonic topological insulators for topological nanophotonics.

Photonic topological insulators are optical structures supporting robust propagation of light at their edges that are topologically protected from scattering. Here we propose the concept of plasmonic topological insulators (PTI) that not only topologically protect light at the lattice edges but also enable their confinement and guidance at the deep-subwavelength scale. The suggested PTI are composed of an evanescently coupled array of metallic nanowires that are modulated periodically along the light propagation direction. The intrinsic loss associated with the PTI is found not to deteriorate their topological protection on the edge modes. The proposed PTI may find interesting applications in nanophotonics, where the tolerance to the fabrication disorders for device applications are essential.