Surface plasmon polaritons in lossy uniaxial anisotropic materials

Anisotropic and lossy media have more complex boundary conditions for the existence of surface plasmon polaritons (SPP) than isotropic media. Boundary conditions are derived for interfaces between a dielectric and a lossy uniaxial material, and the influence of the imaginary part of the dielectric function is addressed. In this case, the momentum excess seems to be no sufficient criterion for SPPs. The angle of Poynting vector to the surface plane is introduced as diagnostic for the attachment of an evanescent wave to the surface, defining the surface-wave character. Predictions of SPPs in graphite are made, including estimates for various propagation lengths.