Resonant inelastic X-ray scattering applied to the electronic structure of strongly correlated systems: The YBCO case

Resonant inelastic soft X-ray scattering is a developing technique well suited to the study of correlation effects in complex materials. We briefly describe its potential for materials science and illustrate its sensitivity with a study of elementary excitations at Cu sites in YBa2Cu3O7−δ as a function of oxygen content. High resolution measurements at the Cu 2p edge reveal structure that, with the help of theoretical models, can be interpreted as due to d–d excitations of the type 3d (x2 − y2) to 3d (3z2 − r2), Zhang–Rice singlets, and changes in the Cu spin configuration.