Valence bands and electron correlation in the high-Tcsuperconductors

Abstract

We consider the x-ray photoemission, inverse photoemission, and $\mathrm{Cu}{L}_3\mathrm{VV}$ Auger spectra of the high-$T_c$ superconductors. We conclude that the on-site correlation energies of the $\mathrm{Cu} 3d$ electrons are large and that the energy of the $\mathrm{Cu} d^8$ configurations is clearly too high for $d^8$ configurations to play a significant role in the ground state.