Two-scale electron structure of copper-oxide superconductors and superconducting pairing mechanism

An acceptor impurity distributed in a crystallographic plane parallel to the superconducting CuO2 plane produces a Coulomb potential in this plane with a large characteristic range. The bottom of the conduction band distorted by this potential plays the role of a secondary potential relief which is manifested in anisotropy of the conductivity and in Raman scattering anomalies. Van der Waals attraction sufficient for the formation of a superconducting gap with a width of tens of millielectronvolts takes place between the holes localized at the secondary relief minima. These phenomena are considered for the YBa2Cu3O(6+x) superconductor. The experimental data confirm the relation between the superconductivity mechanism and the secondary potential relief.