Secondary Retarded Effect in Layered High-Temperature Superconductors

Abstract

Assuming a weak electron-phonon coupling mechanism in the high-temperature superconductivity in copper oxides, the possibility of effective electron-electron interaction mediated by the secondary retarded effect associated with inter- CuO2 layer coupling has been examined. It is pointed out that under the appropriate phonon phase there is an attraction even for |εn,k±q-εn,k|>\\hbarωq, circumventing the conventional BCS restriction.