The evolution of high-T c superconductor electronic structure with doping

Abstract

The model of heterovalence doping of “charge-transfer” insulator proposed to account for the modification of high-T c superconductor (HTSC) properties with doping. According to this model the heterovalence doping of HTSC results in local decreasing of Madelung energy over the doped carrier localization area. It is shown that in such system the transition from insulator to metal state with doping passes through the stage of the formation of the pair electron states (-U-centers) with the single electron energy of the pair orbital placed at the top of oxygen band. Such type of electronic spectrum is supposed to be responsible for both unusual normal properties and high-T c superconductivity in these compounds.