Sub-kelvin Andreev reflection spectroscopy of superconducting gaps in FeSe

TL;DR

This study used sub-kelvin Andreev reflection spectroscopy on FeSe single crystals to identify and analyze two anisotropic superconducting gaps, emphasizing the importance of ultra-low temperatures for detailed gap structure analysis.

Contribution

It provides the first detailed sub-kelvin Andreev reflection analysis of FeSe, revealing two anisotropic gaps and their temperature dependencies.

Findings

Two anisotropic superconducting gaps in FeSe were established.

The gaps follow BCS-like temperature dependencies.

Sub-kelvin temperatures are essential for detailed multiband gap analysis.

Abstract

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.