Identification of the ±s -wave pairing state in iron-pnictide superconductors using the Riedel anomaly

We theoretically propose a method to identify ±s -wave order parameter in recently discovered Fe-pnictide superconductors. Our idea uses the Riedel anomaly in ac-Josephson current through a SI (±S) (single-band s -wave superconductor/insulator/ ±s -wave two-band superconductor) junction. We show that the Riedel peak effect leads to vanishing ac-Josephson current at some values of biased voltage. This phenomenon does not occur in the case when the ±s -wave superconductor is replaced by a conventional s -wave one so that the observation of this vanishing Josephson current would be a clear signature of ±s -wave pairing state in Fe-pnictide superconductors.