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Surface plasmon polaritons in a semi-bounded degenerate plasma: role of spatial dispersion and collisions

Surface plasmon polaritons (SPPs) in a semi-bounded degenerate plasma (e.g., a metal) are studied using the quasiclassical mean-field kinetic model, taking into account the spatial dispersion of the plasma (due to quantum degeneracy of electrons) and electron-ion (electron-lattice, for metals) collisions. SPP dispersion and damping are obtained in both retarded ($ω/k_z\sim c$) and non-retarded ($ω/k_z\ll c$) regions, as well as in between. It is shown that the plasma spatial dispersion significantly affects the properties of SPPs, especially at short wavelengths (less than the collisionless skin depth, $λ\lesssim c/ω_{pe}$). Namely, the collisionless (Landau) damping of SPPs (due to spatial dispersion) is comparable to the purely collisional (Ohmic) damping (due to electron-lattice collisions) in a wide range of SPP wavelengths, e.g., from $λ\sim20$ nm to $λ\sim0.8$ nm for SPP in gold at T=293 K, and from $λ\sim400$ nm to $λ\sim0.7$ nm for SPPs in gold at T=100 K. The spatial dispersion is also shown to affect, in a qualitative way, the dispersion of SPPs at short wavelengths $λ\lesssim c/ω_{pe}$.