Abstract
Superconductors with the composition and have been studied through measurements of x-ray-absorption near-edge structure at the Cu and La edges. Contrary to recent band-structure calculations, we find that the Cu electrons are localized with the copper ions having an integral configuration (2+ valence) independent of dopant concentration. Variation in the area of the "white lines" at the La edges with doping indicates that reduction of the valence charge results in an increase in unoccupied states (probably consisting of holes in the O band) having symmetry relative to the La site. These O holes also appear to have symmetry with respect to the Cu sites.
- Received 5 June 1987
DOI:https://doi.org/10.1103/PhysRevB.36.5263
©1987 American Physical Society