Many-Body Formalism for Photoemission Studies

Abstract

A many-body formalism suitable for application to photoemission or other surface-related problems is developed. It allows one to include, in a simplified way, effects of bulk plasmons, surface plasmons, and electron-hole pairs. A set of optical potentials is obtained which describe the virtual excitation of such modes of the solid. The optical potentials are energy dependent and vary as a function of the distance from the surface. Deep in the crystal they tend to an asymptotic value independent of the location. Characteristic oscillations appear as one approaches the surface region. A cusp at the surface occurs which is followed by a rapid decay of the potential into the vacuum region.