ELECTRONIC BAND-STRUCTURE OF CU3AU - AN ANGLE-RESOLVED PHOTOEMISSION-STUDY ALONG THE [111]-DIRECTION

High-resolution normal photoemission (ARPE) spectra have been recorded for Cu3Au(111) with the use of polarized synchrotron and rare-gas res onance radiation in the photon energy range from 9 to 27 eV. It is for the first time that dispersions of the gold-like bands have been foun d experimentally. Using a fully relativistic layer-KKR photoemission f ormalism, occupied and unoccupied bands as well as one-step-model phot oemission spectra have been calculated. The comparison of calculated s pectra with experimental ones and the observation of direct-transition resonances upon photon energy near the Brillouin zone-center reveal a shift of the unoccupied ground-state bands by about +2.5 eV (self-ene rgy shift). The direct-transition structures in the experimental spect ra have been exploited to determine the dispersions of the occupied ba nds along the [111] direction (LAMBDA line in k space). In order to de termine the wave vector of the experimental direct transitions we used as final state that calculated unoccupied band along [111], which als o exists in pure copper and gold up to about 20 eV above the Fermi ene rgy (''unfolded'' band structure), shifted by +2.5 eV. The experimenta l occupied bands with Cu character are in very good agreement with the ory after shifting the latter by about 0.3 eV to lower energy, whereas somewhat bigger discrepancies exist for the gold-like bands.