Ab initio calculation of the phonon-induced contribution to the electron-state linewidth on the Mg(0001) surface versus bulk Mg

We report a detailed ab initio study of the electron-phonon (e-ph) interaction contribution to the linewidth Γe−ph(ϵk,i) of electron and hole states for bulk magnesium and the Mg(0001) surface. The calculations are based on density functional theory and linear response approach. For bulk Mg, we find a large contribution of optical phonons to the Eliashberg spectral function and to Γe−ph(ϵk,i). The e-ph coupling parameter λ at the Fermi level (mass enhancement parameter) has been found to be λ=0.30. In the case of the surface, we have focused on the study of the ¯Γ and ¯M surface states for which we find λ=0.28 and λ=0.38, respectively. We show an important role of the Rayleigh vibrational mode in the e-ph coupling in the ¯Γ surface state. These results are in a very good agreement with tunneling spectroscopic data and recent photoemission measurements of λ.This work was partially supported by the University of the Basque Country, the Departamento de Educación del Gobierno Vasco, and MCyT Grant No. FIS 2004-06490-C03-01.Peer reviewe