Metallic, band-like behaviour of EuBa2Cu3O6.7 as seen from UPS spectra Comparison with band calculations

Valence band photoemission spectra of single crystals of EuBa2Cu3O6.7, cleaved and measured at T=20 K, are presented. A stable Fermi edge is observed, whose amplitude is ≈10% of the maximum valence band intensity. This suggests metallic behavior. Except for 1 eV shift toward higher binding energy, the results compare favorably with previous band calculations, and hint at a re-examination of theories based purely on a localized electronic structure. There is evidence for both Cu-3d and O-2p occupation at EF, as predicted by band calculations. © 1988