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

## TL;DR

This study provides direct evidence of two distinct superconducting gaps in FeSe$_{0.5}$Te$_{0.5}$ using Andreev spectroscopy and critical field measurements, supporting a two-band superconductivity model.

## Contribution

First direct measurement of two superconducting gaps in FeSe$_{0.5}$Te$_{0.5}$ using multiple techniques, confirming two-band superconductivity with detailed gap temperature dependences.

## Key findings

- Identified two superconducting gaps: approximately 3.3-3.4 meV and 1 meV.
- Two-band model accurately describes the experimental data.
- Strong intraband and moderate interband electron-boson coupling.

## 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.