From the Shockley surface state on Cu(111) tosp-like surface resonances onCu3Au(111)

Abstract

In an angle-resolved ultraviolet photoemission spectroscopy study on ordered ${\mathrm{Cu}}_{3}\mathrm{Au}(111)$ we have observed two $\mathrm{sp}$-like surface resonances at 0.4 and 1.0 eV below the Fermi energy around the center of the surface Brillouin zone. Bulk and slab charge densities were calculated self-consistently by a full-potential linearized augmented plane method and employed to construct---via a nonlocal density approximation to exchange and correlation---a real part of the effective one-electron potential, which we subsequently used in relativistic layer Korringa-Kohn-Rostoker calculations to obtain the quasiparticle bulk-band structure, the ${k}_{\ensuremath{\Vert}}$- and layer-resolved density of states and photoemission spectra. For Cu(111), we thus obtained the Shockley surface state and its dispersion in good agreement with experimental data. For ${\mathrm{Cu}}_{3}\mathrm{Au}(111),$ we retrieved our two measured surface features and their dispersions with ${k}_{\ensuremath{\Vert}}.$ The feature at 0.4 eV, which corresponds to the Shockley state on Cu(111), is substantially broadened due to hybridization with bulk states. The feature at 1.0 eV, although also degenerate with a bulk band, is comparatively sharp because of different symmetry types.