Model prediction of high-temperature pi-states in iron pnictide superconductor-insulator-superconductor Josephson junctions

We study the Josephson effect in s±Is± junctions made by two-bands reversed-sign s-wave (s±) superconductive materials. We derive a spectral equation providing the bound Andreev energy states at the interface. The energy spectrum depends on a parameter accounting for the weight of the second band with respect to the first one. For selected values of this parameter and the tunnel barrier amplitude, we predict various features of the Josephson current, among which a possible high-temperature doubly degenerate junction ground state (?-state) and a $\pi \rightarrow 0$ crossover with decreasing temperature.