Universal self-amplification channel for surface plasma waves

Abstract

We present a theory of surface plasma waves (SPWs) in metals with arbitrary electronic collision rate ${\ensuremath{\tau}}^{\ensuremath{-}1}$. We show that there exists a universal intrinsic amplification channel for these waves, subsequent to the interplay between ballistic motions and the metal surface. We evaluate the corresponding amplification rate ${\ensuremath{\gamma}}_{0}$, which turns out to be a sizable fraction of the SPW frequency ${\ensuremath{\omega}}_{s}$. We also find that the value of ${\ensuremath{\omega}}_{s}$ depends on surface scattering properties, in contrast with the conventional theory.