DAMPING OF SURFACE PLASMON-PHONON POLARITONS

The influence of the bulk damping in polar crystals on the elementary properties of surface polaritons (SP) of a mixed plasmon-phonon type is studied theoretically. Two different methods for the calculation of SP damping are used. These methods are shown to give the same results. Definite combinations of the plasmon and phonon damping constants are found to lead to a minimum in the damping and a maximum in the planar propagation length versus wave vector dependences. An increase in the SP energy dissipation due to an increase in the damping constants of elementary excitations in a crystal and the SP scattering by surface roughness give rise to a reduction of the SP frequency, but the shape of the dispersion curve changes differently, what can be distinguished experimentally.