MULTIPLE PLASMON SATELLITES IN NA AND AL SPECTRAL FUNCTIONS FROM AB-INITIO CUMULANT EXPANSION

The valence photoemission spectra of alkali metals exhibit multiple pl asmon satellite structure. The calculated spectral functions within th e GW approximation show only one plasmon satellite at too large bindin g energy. In this Letter we use the cumulant expansion approach to obt ain the spectral functions of Na and Al from ab initio calculations in cluding the effects of band structure. The GW spectral functions an dr amatically improved and the positions of the multiple plasmon satellit es are in very good agreement with experiment while their intensities cannot be explained from intrinsic effects only.