Shapiro steps in heterotic SIS multi-tunneling-channel Josephson junctions; Identification of s-wave in iron-pnictide superconductors

Ota, Yukihiro; Nakai, Noriyuki; Nakamura, Hiroki  ; Machida, Masahiko  ; Inotani, Daisuke*; Ohashi, Yoji*; Koyama, Tomio*; Matsumoto, Hideki*

An enormous amount of studies has been devoted to the identification of the pairing symmetry in iron-based superconductors. In the paper, we focus on a heterotic (multiband) superconductor- insulator-(single-band)superconductor junction. First, we derive the Amgegaokar-Baratoff relation. We evaluate a theoretical lowerbound of for s-wave without sign change, which may correspond to a upper bound for s-wave. Next, we discuss how a fluctuation of relative phases between multiple gaps and the pairing symmetry correct the Shapiro step, e.g., the step height and the step position. On the basis of these results, we propose a conventional and direct method to identify the s-wave symmetry.