T. E. Kuzmicheva, S. A. Kuzmichev, A. D. Il'ina, I. A. Nikitchenkov, A. I. Shilov, E. O. Rakhmanov, I. V. Morozov, “Single-gap superconductivity of (K$_{0.8}$Na$_{0.2}$)$_{0.9}$Fe$_{1.7}$Se$_2$ and K$_{0.8}$Fe$_{1.7}$(Se$_{0.73}$S$_{0.27}$)$_2$ selenides determined using multiple Andreev reflection effect spectroscopy”, Fizika Tverdogo Tela, 2025, Volume 67, Issue 6,Pages 1069

XXIX International Symposium "Nanophysics and Nanoelectronics", Nizhny Novgorod, March 10-14, 2025
Superconductivity

Single-gap superconductivity of (K$_{0.8}$Na$_{0.2}$)$_{0.9}$Fe$_{1.7}$Se$_2$ and K$_{0.8}$Fe$_{1.7}$(Se$_{0.73}$S$_{0.27}$)$_2$ selenides determined using multiple Andreev reflection effect spectroscopy

T. E. Kuzmicheva^a, S. A. Kuzmichev^ab, A. D. Il'ina^a, I. A. Nikitchenkov^ab, A. I. Shilov^a, E. O. Rakhmanov^ac, I. V. Morozov^c

^a P. N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow
^b Lomonosov Moscow State University, Faculty of Physics
^c Lomonosov Moscow State University, Faculty of Chemistry

Abstract: We have comprehensively studied the structure of the superconducting order parameter of (K$_{0.8}$Na$_{0.2}$)$_{0.9}$Fe$_{1.7}$Se$_2$ and K$_{0.8}$Fe$_{1.7}$(Se$_{0.73}$S$_{0.27}$)$_2$ iron selenides with critical temperatures $T_c\approx$ 27–31 K. Using incroherent multiple Andreev reflection effect spectroscopy of planar “break-junctions”, in both compounds a development of a single-gap superconductivity and a bulk nature of the observed superconducting gap were shown, its magnitude and temperature dependence have been determined. The characteristic ratio 2$\Delta (0)/k_{\mathrm{B}}T_c\approx$ 4.1–4.6 obtained for both compounds is almost similar for both compounds and points to a strong coupling in the electron bands.

Keywords: high-temperature superconductivity, iron-containing superconductors, tunneling spectroscopy, superconducting order parameter.

Received: 06.03.2025
Revised: 06.03.2025
Accepted: 05.05.2025

DOI: 10.61011/FTT.2025.06.60958.8HH-25