Surface Plasmon-Polaritons and Transverse Spin Angular Momentum at the Boundary of a Hyperbolic Metamaterial with an Arbitrarily Oriented Optic Axis

The features of plasmon-polaritons excited at the boundary of a hyperbolic metamaterial and a dielectric are studied in the case where the optic axis is oriented at an angle to the interface. It is shown that in the metamaterial the phase velocity of the plasmon-polariton is directed at a certain angle to the boundary. The possibility is established and the conditions are determined for localization of plasmon-polaritons at the boundary of both type I and type II hyperbolic metamaterials. A surface plasmon-polariton localized at the interface of an isotropic dielectric and a hyperbolic metamaterial is shown to have transverse spin of a magnitude that depends on the wavelength of the exciting radiation, the orientation of the optic axis, and the dielectric properties of the adjoining media.