Mechanism of the superconductivity of twinning planes

The problem of calculation of Tc of a superconductor with a planar defect is solved subject to fairly general assumptions about the defect. The equivalence of superconducting properties is demonstrated for a topological defect of a twinning lane type and a scattering defect in the form of a monolayer of foreign atoms. A system of nonlinear equations for a localized superconductivity is derived. It is shown that in addition to a phenomenological Buzdin-Bulaevskii picture, it is possible to provide a different explanation which alters radically the interpretation of the experimental results of Khaikin and Khlyustikov and, in contrast to the former, can give reasonable values of microscopic parameters. Systems of periodically distributed planar defects are investigated. An analysis is made of the possibility of reaching high values of Tc in a system of this kind because of Van Hove singularities in the spectrum of two-dimensional Tamm energy bands