Valley-Polarized Hyperbolic-Exciton-Polaritons in 2D Semiconductors

Polaritons are light-matter quasi-particles in the form of optical excitations, which play a major role in nanophotonics owing to their ability to control, confine and enhance light at the nanoscale. Even stronger confinement can be achieved by hyperbolic polaritons, i.e. polaritons supported by materials with an hyperbolic dispersion. Here. we predict the existence of hyperbolic-exciton-polaritons (HEPs) in 2D semiconductors of transition-metal-dichalcogenides (TMDs) at visible frequencies. We show that hyperbolicity can be induced in the layered material owing to the behavior of the excitons supported by the TMD, therefore leading to the existence of HEPs. We derive the HEPs dispersion relation, analyzing their confinement and loss properties and finding the HEPs’ wavelengths are about two orders of magnitude smaller than the corresponding free-space wavelength. Furthermore, we show that the existing HEPs are coupled to the valley degree-of-freedom, leading to a hyperbolic spin-valley hall effect.