Insulator-Conductor Transition in Doped HTS as a Consequence of -U-Centers Generation

Abstract

It is supposed that the transition from insulator to metal state under doping in high-T c superconductors (HTS) passes through the stage of -U-centers formation, which arise on the neighbor Cu ions when the definite spatial arrangement of the doping atoms is realized. In this doping region the free hole carriers (just as in hole-, so in electron-doped HTS) are generated when electron pairs transfer from the oxygen band into -U-centers.