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Ota, Yukihiro; Nakai, Noriyuki; Nakamura, Hiroki; Machida, Masahiko; Inotani, Daisuke*; Ohashi, Yoji*; Koyama, Tomio*; Matsumoto, Hideki*
Physical Review B, 81(21), p.214511_1 - 214511_6, 2010/06
Times Cited Count：32 Percentile：75.43(Materials Science, Multidisciplinary)An extension of the Ambegaokar-Baratoff relation to a superconductor-insulator-superconductor (SIS) Josephson junction with multiple tunneling channels is derived. Applying the resultant relation to a SIS Josephson junction formed by an iron-based (five-band) and a single-band Bardeen-Cooper-Schrieffer (BCS) type superconductors, a theoretical bound of the Josephson critical current (
) multiplied by the resistance of the junction (
) is given. We reveal that such a bound is useful for identifying the pairing symmetry of iron-pnictide superconductors. One finds that if a measured value of 
is smaller than the bound then the symmetry is 
-wave, and otherwise 
-wave without any sign changes. In addition, we stress that temperature dependence of is sensitive to the difference of the gap functions from the BCS type gap formula in the above heterojunction.
s-wave in iron-pnictide superconductorsOta, Yukihiro; Nakai, Noriyuki; Nakamura, Hiroki; Machida, Masahiko; Inotani, Daisuke*; Ohashi, Yoji*; Koyama, Tomio*; Matsumoto, Hideki*
no journal, ,
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.
-wave in iron-based superconductorsOta, Yukihiro; Nakai, Noriyuki; Nakamura, Hiroki; Machida, Masahiko; Inotani, Daisuke*; Ohashi, Yoji*; Koyama, Tomio*; Matsumoto, Hideki*
no journal, ,
An enormous amount of studies has been devoted to the identification of the pairing symmetry in iron-based superconductors. We show a theory of Josephson junctions with multi-gap superconductors. We focus on a heterotic (multi-band)superconductor- insulator-(one-band)superconductor junction. We derive the Ambegaokar-Baratoff relation. We evaluate a lower bound of for -wave without sign change, which may correspond to a upper bound for -wave. Next, we discuss how a fluctuation of relative phases between the gaps and the symmetry modify the Shapiro step. Thus, we propose a direct method to identify -wave.
