Dynamical response of correlated electrons in solids probed by inelastic scattering experiments: an ab initio theoretical perspective

We present results of ab initio theoretical investigations of the excitatio n spectra of correlated electrons in metals (Al, K, and Li) and their inter play with inelastic scattering experiments. We resolve various anomalies co ntained in the data, which were originally viewed as signatures of strong d ynamical electronic correlations; we show that, instead, the anomalies are due to band-structure effects. The underlying theoretical framework in our density-response calculations is time-dependent density-functional theory; with this scheme we discuss the lifetime of the K plasmon, and the dynamica l structure factor of Al. From a self-consistent solution of the Dyson equa tion in the GW approximation for the electron self-energy, we discuss the e lectron momentum density in Li. Our results and methods point to a new way of thinking about electronic excitations in real materials. The main challe nge ahead is the proper treatment of dynamical correlations for realistic r epresentations of the band structure. (C) 2000 Published by Elsevier Scienc e Ltd. All rights reserved.