Hybrid surface plasmon polaritons localized at anisotropic metasurface

We show that surface plasmon polaritons (SPP) localized at anisotropic conductive interfaces possess a number of unique features. The interface is described as a two-dimensional current distribution of zero thickness by using a conductivity tensor. The dispersion of such SPP consists of two branches of hybrid TE-TM polarized modes. We reveal that, in contrast to bulk plane waves and conventional surface plasmons at isotropic interfaces, the spin of the hybrid surface waves can be engineered to have an arbitrary angle with the propagation direction. This property allows to tailor directivity of surface waves. In the hyperbolic regime of the metasurface, there exists a range of allowed angles for them to propagate, resembling well-known D'yakonov surface waves. This property depends on the relation between the conductivities along two principle directions in the plane of the metasurface.