The effect of phonon-mediated charge transfer and internal proximity effect on the properties of multigap cuprate superconductors

The theoretical model capable of calculating the superconducting properties (e.g. Tc, energy gaps, etc) of materials such as Y1Ba2Cu3O7 which consist of two conducting subsystem (planes and chains) is developed. The system is characterized by two energies gaps. The interplay of two channels (phonon-mediated processes and the intrinsic proximity effect) inducing the superconducting state in the chains is studied. The proximity effect combined with the phonon-mediated channel appears to be favorable for superconductivity. The theory describes the effect of the oxygen ordering on Tc and the induced gap and allows us to explain a number of experiments including the plateau in Tc versus oxygen, the large residual microwave losses, zero-bias anomalies and the temperature dependence of the penetration depth. (orig.)