Angle-resolved photoemission investigation of the electronic band properties of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{x}}$(001)

The electronic energy-band properties of epitaxially grown ${\mathrm{YBa}}_2$ ${\mathrm{CuO}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{x}}$(001) single-crystal thin films have been investigated by angle-resolved ultraviolet photoemission spectroscopy (ARUPS) with synchrotron radiation as the light source. The (001) surfaces exhibit sharp (1×1) low-energy electron-diffraction patterns. Our ARUPS data show a clear Fermi edge and dispersive nature of the valence bands, suggesting the validity of the band concept for this oxide. We determined energy-band dispersion along the Γ-X-M-Γ directions in the bulk Brillouin zone. The experimental results are compared with the existing ground-state band calculations.