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

In this work, 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.