Theoretical proposal of a method to identify the pairing symmetry of Fe-pnictide superconductors using ac-josephson effect

We theoretically propose a method to detect ±s-wave state in newly discovered Fe-pnictide superconductors, using ac Josephson current through a single-band superconductor/insulator/±s-wave superconductor ( S / I / ± S ) junction. We show that, because of the Riedel anomaly, the ac Josephson current vanishes at some values of biased voltage across the junction. This phenomenon does not occur without the sign difference of order parameters in the two band superconductor, so that the observation of the vanishing ac Josephson current would be a clear signature of ±s-wave pairing symmetry in Fe-pnictides.