Boundary conditions for the junction of a normal metal with multiband superconductors with unusual types of superconducting pairing

The boundary conditions for the junction of a normal metal with multiband superconductors with unusual types of superconducting pairing have been obtained on the basis of the tight-binding equations. These boundary conditions have been obtained beyond the effective mass approximation. They make it possible to take into account the nonparabolic and anisotropic spectrum of the normal excitations in a superconductor and their multiband structure, as well as unusual types of symmetries of the superconducting order parameter. These boundary conditions have been used to calculate the conductivities of junctions of a normal metal with a high-temperature superconducting pnictide for different orientation angles of the interface with respect to the pnictide crystallographic axes.