Linear decrease of critical temperature with increasing Zn substitution in the iron-based superconductor BaFe1.89-2xZn2xCo0.11As2

TL;DR

This study investigates how nonmagnetic Zn impurity substitution linearly suppresses the critical temperature in BaFe1.89Co0.11As2 superconductors, challenging the s(+-)-wave pairing model and suggesting alternative symmetry models.

Contribution

It provides experimental evidence that Zn substitution suppresses Tc linearly, with implications for understanding pairing symmetry in Fe-based superconductors.

Findings

Tc decreases linearly with Zn content

Tc disappears at about 8% Zn substitution

The suppression rate is lower than expected for s(+-)-wave model

Abstract

The nonmagnetic impurity effect is studied on the Fe-based BaFe1.89Co0.11As2 superconductor (Tc = 25 K) with Zn substitution for Fe up to 8 at. %, which is achieved by means of high-pressure and high-temperature heating. Tc decreases almost linearly with increasing the Zn content and disappears at ~8 atomic %, being different in the shared phenomenology of the early Zn doping studies, where Tc decreases little. The Tc decreasing rate, however, remains much lower (3.63 K/%) than what is expected for the s(+-)-wave model, implying the model is unlikely. Another symmetry model such as the non-sign reversal s-wave model may better account for the result.