Nature of the valence photoemission features of single-crystalYBa2Cu3O7−x

Abstract

The photoemission spectra of the high-temperature superconductor $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-x}$ exhibit a feature 9.5 eV below the Fermi level, whose nature has been controversial and that was attributed to contamination by some authors. Data taken for the first time on cleaved single crystals show that the feature is not related to contamination. A study of its behavior suggests that it is consistent with Wendin's explanation in terms of a two-hole satellite of a primarily oxygen-related photoemission feature 2.5 eV below the Fermi level.