Electronic States in High-T_c Copper-Oxide Superconductors

Abstract

The electronic states in the CuO₂-layer have been studied by using the p-d model with the help of the bosonic technique for treating the local electronic correlation properly. What have been found are: at sufficiently low temperature the electronic states form coherent bands but there is a significant difference between the effects of electron doping and those of hole doping. In particular, the hole doping brings about a new band around the Fermi level inside the energy gap and intensity of the band increases as the number of holes increases. These band schemes may well explain the experiments.