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

Abstract

Valence band photoemission spectra of single crystals of EuBa,Cu,O,.,, 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 a 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 0-2~ occupation at E,, as predicted by band calculations.