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

Abstract

We theoretically propose a method to identify $\ifmmode\pm\else\textpm\fi{}s$-wave order parameter in recently discovered Fe-pnictide superconductors. Our idea uses the Riedel anomaly in ac-Josephson current through a $\text{SI}(\ifmmode\pm\else\textpm\fi{}\text{S})$ (single-band $s$-wave superconductor/insulator/$\ifmmode\pm\else\textpm\fi{}s$-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 $\ifmmode\pm\else\textpm\fi{}s$-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 $\ifmmode\pm\else\textpm\fi{}s$-wave pairing state in Fe-pnictide superconductors.