X-ray absorption of YBa2Cu3O7: A band picture

Abstract

Using band-structure theory, we calculate the O 1s and Cu 2p x-ray-absorption spectra of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$. The former spectra are in rather good agreement with experiment, showing that the peaks in the low-energy region are due to the van Hove singularity in the chain band. Using core-exciton theory, we argue that this van Hove singularity can survive the strong Cu 2p–3d Coulomb interaction, giving rise to the ‘‘satellite’’ in the chain Cu 2p spectrum.