Microscopic theory for phase-sensitive experiments to determine the symmetry of the order parameter in Fe-based superconductors
We present a microscopic theory for the dc Josephson current, based on the construction of a coherent temperature Green's function in the tight-binding approximation, in junctions with multiband superconductors. This theory is applied to junctions with a multiband Fe-based superconductor (FeBS) described by s+/- -wave and s++ -wave order parameter symmetries, which is probably realized in FeBS. For the first time, phase dependences of the Josephson current have been calculated for different directions of an interface with respect to crystallographic axes of FeBS. The present approach is also suitable for a consistent description of the Josephson transport in structures with topological superconductors.