Bulk and surface electronic states of ordered Cu3Au(001): An angle-resolved photoemission investigation

We have performed an angle-resolved ultraviolet photoemission spectroscopy (ARUPS) investigation of ordered Cu3Au(001) at room temperature using He resonance and synchrotron radiation. The positions of upper Cu-like bulk bands near the center Gamma of the bulk Brillouin zone (BZ) and the dispersion of the upper sp band along the Delta line have been determined using bulk-sensitive photon energies 10 eV less than or equal to hv greater than or equal to 15 eV. Except for a downward shift, the calculated bulk bands are in excellent agreement with experiment. Around the centers <(Gamma)over bar> of the surface BZ, we have identified three new surface states in the energy region of the Au-like states and several surface-sensitive features in the Cu-like region below the known surface state on top of the Cu-like bulk d bands. These states strongly contribute to the ARUPS spectra for hv greater than or equal to 20 eV. The wealth of surface features found is in overall agreement with a recent surface electronic structure calculation [S. Halilov, H. Gollisch, E. Tamura and R. Feder, J. Phys.: Condens. Matter 5, 4711 (1993)]. More detailed information is obtained by comparing the experimental spectra with theoretical ones calculated by a relativistic one-step model formalism.