Cluster analyses of electronic states in electron-doped copper oxide superconductors

Abstract

We examine the electronic states in the electron-doped copper oxide superconductors, Nd2−xCexCuO4, with the cluster model approach. In the oxides, the Cu-4s orbital plays an important role under electron-doping. We find that in a possible parameter range the doping causes a composite state with spin-singlet, which is made of Cu-3d, Cu-4s and O-2p orbitals. The Cu-3d valence-band photoemission spectra are calculated.