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

TL;DR

This paper investigates how spatial dispersion and collisions influence surface plasmon polaritons in degenerate plasmas, revealing significant effects on their dispersion and damping, especially at short wavelengths relevant for metals like gold.

Contribution

It provides a comprehensive analysis of SPP dispersion and damping considering both spatial dispersion and collisions in degenerate plasmas, highlighting their combined impact at nanometer scales.

Findings

Spatial dispersion significantly affects SPP properties at wavelengths below the collisionless skin depth.

Landau damping due to spatial dispersion can be comparable to collisional damping in certain wavelength ranges.

Short-wavelength SPP dispersion is qualitatively altered by spatial dispersion effects.

Abstract

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 ($\omega/k_z\sim c$) and non-retarded ($\omega/k_z\ll c$) 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, $\lambda\lesssim c/\omega_{pe}$). 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 $\lambda\sim20$ nm to $\lambda\sim0.8$ nm for SPP in gold at T=293 K, and from $\lambda\sim400$ nm to $\lambda\sim0.7$ 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 $\lambda\lesssim c/\omega_{pe}$.