Plasma oscillations of electron gases

Abstract

A unifying concept, that of the frequency- and wave number-dependent longitudinal dielectric constant epsilon (k, omega ), is described which offers a simple way to tie together the theoretical approaches to the electron gas and to describe the plasma oscillations. When epsilon (k, omega ) = 0, it permits the existence of an oscillatory mode with an associated build-up of charge density and electric field potential. The properties of plasmons (quantized plasma waves) were also investigated using the random phase approximation approach. Experimental evidence of plasmons as a well-defined excitation mode in electron systems, which comes from characteristic energy loss experiments in solids, is reviewed. (M.C.G.)