Loss ofπ-junction behavior in an interacting impurity Josephson junction

Using a generalization of the noncrossing approximation which incorporates Andreev reflection, we study the properties of an infinite-U Anderson impurity coupled to two superconducting leads. In the regime where Δ and TK are comparable, we find that the position of the subgap resonance in the impurity spectral function develops a strong anomalous phase dependence---its energy is a minimum when the phase difference between the superconductors is equal to π. Calculating the Josephson current through the impurity, we find that π-junction behavior is lost as the position of the bound state moves above the Fermi energy.