Large decrease in the critical temperature of superconducting LaFeAsO0.85 compounds doped with 3% atomic weight of nonmagnetic Zn impurities

TL;DR

This study demonstrates that a small amount of nonmagnetic Zn impurities significantly suppresses the superconducting critical temperature in LaFeAsO0.85, supporting a sign-reversal s-wave pairing mechanism in Fe pnictide superconductors.

Contribution

It provides experimental evidence of rapid Tc suppression by nonmagnetic impurities, aligning with the sign-reversal s-wave pairing theory in Fe-based superconductors.

Findings

Tc decreases by approximately 9 K per 1% Zn doping

Suppression of superconductivity linked to pair-breaking effects

Supports sign-reversal s-wave pairing model

Abstract

We observed a large decrease of Tc by no more than 3 at.% of Zn doped to the optimized superconductor LaFeAsO0.85 (Tc = 26 K), confirmed by measurements of electrical resistivity, magnetic susceptibility, specific heat, M\"ossbauer spectroscopy, Hall coefficient, and an electron probe micro-analysis. The rate ~9 K/% is remarkably higher than observations regarding nonmagnetic impurities. The Tc suppression is likely due to pair-breaking caused by scatterings associated with highly localized electronic state of Zn doped into the Fe2As2 layer. If this is true, the Zn result well accords with the theoretical prediction that suggests a sign reversal s-wave pairing model for the Fe pnictide superconductors, unlike other nonmagnetic impurity results.