The Effect of Interface Potential Barriers on Boundary Conditions in the Theory of Dirty Inhomogeneous Superconducting Systems Near Transition Temperature

A theoretical treatment of the superconductor-normal metal contact with interface potential barrier is presented in the dirty limiting case. Our result for the kernel of the linearized self-consistency condition allows near transition temperature the determination of boundary conditions and the behaviour of Usadel's function at interfaces. This represents a microscopic derivation of the so-called “extended” de Gennes boundary condition. With the help of a variational procedure an expression is derived for the Ginsburg-Landau extrapolation length of dirty SN systems with interface potential barrier.