Sub-kelvin Andreev reflection spectroscopy of superconducting gaps in FeSe
D.L. Bashlakov1, N.V. Gamayunova1, L.V. Tyutrina1, J. Kačmarčik2, P. Szabó2, P. Samuely2, and Yu.G. Naidyuk1
1B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Nauki Ave., Kharkiv 61103, Ukraine
E-mail: bashlakov @ilt.kharkov.ua
2Centre of Low Temperature Physics, Institute of Experimental Physics, Slovak Academy of Sciences Watsonova 47, SK-04001 Košice, Slovakia
Received September 3, 2019, published online September 27, 2019
Point contact Andreev reflection studies have been conducted on FeSe single crystals by lowering the temperatures down to 0.5 K. The point contact Andreev reflection spectra were analyzed in the framework of the two-band model. As a result, the presence of two anisotropic superconducting gaps in FeSe were certainly established and their BCS-like temperature dependencies were obtained. The weights of each gap have been determined and the anisotropy parameter has been calculated. It is shown, that sub-kelvin temperatures are necessary to ascertain details of the superconducting gap structure, especially for multiband materials when Andreev reflection spectroscopy is applied.
Key words: Andreev reflection, point contact, superconducting gap structure.