Band structure effects on the Be(0001) acoustic-surface-plasmon energy dispersion

We report first-principles calculations of acoustic surface plasmons on the (0001) surface of Be, as obtained in the random-phase approximation of many-body theory. The energy dispersion of these collective excitations has been obtained along two symmetry directions. Our results show a considerable anisotropy of acoustic surface plasmons, and underline the capability of experimental measurements of these plasmons to {it map} the electron-hole excitation spectrum of the quasi two-dimensional Shockley surface state band that is present on the Be(0001) surface.

Theory of inelastic lifetimes of surface-state electrons and holes at metal surfaces

After the early suggestion by John Pendry to probe unoccupied bands at surfaces through the time reversal of the photoemission process, the inverse-photoemission technique yielded the first conclusive experimental evidence for the existence of image-potential bound states at metal surfaces and has led over the last two decades to an active area of research in condensed-matter and surface physics. Here we describe the current status of the many-body theory of inelastic lifetimes of these image-potential states and also the Shockley surface states that exist near the Fermi level in the projected bulk band gap of simple and noble metals. New calculations of the self-energy and lifetime of surface states on Au surfaces are presented as well, by using the $GWGamma$ approximation of many-body theory.

Self-energy and lifetime of Shockley and image states on Cu(100) and Cu(111): Beyond the GW approximation of many-body theory

We report many-body calculations of the self-energy and lifetime of Shockley and image states on the (100) and (111) surfaces of Cu that go beyond the $GW$ approximation of many-body theory. The self-energy is computed in the framework of the GWGamma approximation by including short-range exchange-correlation (XC) effects both in the screened interaction W (beyond the random-phase approximation) and in the expansion of the self-energy in terms of W (beyond the GW approximation). Exchange-correlation effects are described within time-dependent density-functional theory from the knowledge of an adiabatic nonlocal XC kernel that goes beyond the local-density approximation.

Simple dynamic exchange-correlation kernel of the uniform electron gas

We propose a simple dynamic exchange-correlation kernel of the uniform electron gas. We model the reduction of the electron-electron interaction due to short-range exchange-correlation effects by introducing a frequency-dependent error-function effective interaction. By imposing the fulfillment of the compresibility and the third-frequency-moment sum rules, as well as the correct asymptotic behavior at large wave vectors, we find an accurate and simple dynamic exchange-correlation kernel that accurately reproduces the wave-vector analysis and the imaginary-frequency analysis of the correlation energy of the uniform electron gas.