Estimation of intraband and interband relative coupling constants from temperature dependences of the order parameter for two-gap superconductors

Abstract

We present temperature dependences of the large and the small superconducting gaps measured directly by SnS-Andreev spectroscopy in various Fe-based superconductors and MgB${}_2$. The experimental ${\Delta }_{L,S}(T)$ are well-fitted with a two-gap model based on Moskalenko and Suhl system of equations (supplemented with a BCS-integral renormalization). From the the fitting procedure, we estimate the key attribute of superconducting state \textemdash relative electron-boson coupling constants and eigen BCS-ratios for both condensates. Our results evidence for a driving role of a strong intraband coupling in the bands with the large gap, whereas interband coupling is rather weak for all the superconductors under study.

arXiv comment7 pages, 5 figures, accepted to J. Supercond. Novel Magn

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• Direct Evidence of Two Superconducting Gaps in FeSe${}_{0.5}$Te${}_{0.5}$: SnS-Andreev Spectroscopy and Lower Critical Field
• Collective excitations in two-band superconductors