Electron energy-loss and x-ray absorption spectroscopy of cuprate superconductors and related compounds

Abstract

O1s and Cu2p absorption edges of cuprate high- T c superconductors (HTSC) and related compounds measured by electron energy-loss spectroscopy (EELS) and X-ray absorption spectroscopy (XAS) are reviewed. Since these edges are related to the site-selective unoccupied density of states, they provide important information on the normal-state electronic structure of HTSCs. In particular they can determine the character of the charge carriers of both the p- and n-type doped cuprates and they indicate that correlation effects are important in these systems. Orientation dependent EELS and polarization dependent XAS measurements on cuprate single crystals provide information on the symmetry of the hole states in the CuO 2 planes and block layers of the HTSCs. The results impose strong constraints on theories of high- T c superconductivity which are based on charge carriers in out-of-plane orbitals.