Direct Evidence of Two Superconducting Gaps in FeSe$_{0.5}$Te$_{0.5}$: SnS-Andreev Spectroscopy and Lower Critical Field

T. E. Kuzmicheva; S. A. Kuzmichev; A. V. Sadakov; A. V. Muratov; A. S. Usoltsev; V. P. Martovitsky; A. R. Shipilov; D. A. Chareev; E. S. Mitrofanova; V. M. Pudalov

doi:10.1134/s0021364016240048

arXiv · 1705.06140

Direct Evidence of Two Superconducting Gaps in FeSe$_{0.5}$Te$_{0.5}$: SnS-Andreev Spectroscopy and Lower Critical Field

T. E. Kuzmicheva·S. A. Kuzmichev·A. V. Sadakov·A. V. Muratov·A. S. Usoltsev·V. P. Martovitsky·A. R. Shipilov·D. A. Chareev·E. S. Mitrofanova·V. M. Pudalov

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Abstract

We present direct measurements of the superconducting order parameter in nearly optimal FeSe$_{0.5}$Te$_{0.5}$ single crystals with critical temperature $T_C \approx 14$ K. Using intrinsic multiple Andreev reflection effect (IMARE) spectroscopy and measurements of lower critical field, we directly determined two superconducting gaps, $\Delta_L \approx 3.3 - 3.4$ meV and $\Delta_S \approx 1$ meV, and their temperature dependences. We show that a two-band model fits well the experimental data. The estimated electron-boson coupling constants indicate a strong intraband and a moderate interband interaction.

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T. E. Kuzmicheva, S. A. Kuzmichev, A. V. Sadakov, A. V. Muratov, A. S. Usoltsev, V. P. Martovitsky, A. R. Shipilov, D. A. Chareev, E. S. Mitrofanova, V. M. Pudalov. 2017-05-17. Direct Evidence of Two Superconducting Gaps in FeSe$_{0.5}$Te$_{0.5}$: SnS-Andreev Spectroscopy and Lower Critical Field. https://doi.org/10.1134/s0021364016240048

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