Self-energy and inelastic lifetimes of surface-state electrons and holes in metals

A metal surface generates electron states that do not exist in a bulk metal. These so-called surface states can be classified into two categories, crystal-induced (intrinsic) states and image-potential-induced (image) states. Here we present. a survey of current investigations on the origin of the decay of these surface states. Inelastic lifetimes are obtained from the knowledge of the quasiparticle self-energy, which we compute, within the GW approximation of many-body theory, by going beyond a free-electron description of the surface. Surface-state lifetimes in noble metal surfaces are presented. Our results show that actual lifetimes are highly sensitive to the details of the surface response and to the presence of the intrinsic surface state itself.