Universal scaling behavior of the upper critical field in strained FeSe0.7Te0.3 thin films

TL;DR

This study demonstrates that the slope of the upper critical field in strained FeSe0.7Te0.3 thin films scales linearly with Tc, revealing a universal behavior in iron-based superconductors linked to multiband pairing mechanisms.

Contribution

It uncovers the universal linear scaling of -dHc2/dT with Tc in FeSe0.7Te0.3, supporting the multiband superconductivity model with interband pairing.

Findings

-dHc2/dT scales linearly with Tc

Universal behavior observed across iron-based superconductors

Supports sign-changing s+- pairing mechanism

Abstract

Revealing the universal behaviors of iron-based superconductors (FBS) is important to elucidate the microscopic theory of superconductivity. In this work, we investigate the effect of in-plane strain on the slope of the upper critical field Hc2 at the superconducting transition temperature Tc (i.e. -dHc2/dT) for FeSe0.7Te0.3 thin films. The in-plane strain tunes Tc in a broad range, while the composition and disorder are almost unchanged. We show that -dHc2/dT scales linearly with Tc, indicating that FeSe0.7Te0.3 follows the same universal behavior as observed for pnictide FBS. The observed behavior is consistent with a multiband superconductivity paired by interband interaction such as sign change s+- superconductivity.