Surface-Plasmon Dispersion: A Comparison of Microscopic and Hydrodynamic Theories

Abstract

The hydrodynamic theory of the electron gas, first applied to surface plasmons in metals by Ritchie, is critically examined using the equation of motion for the Wigner distribution function in the random-phase approximation (RPA). It is found that the theory does not agree with the RPA in the case of surface plasmons, though it does for bulk plasmons.