Contrasting Pair-Breaking Effects by Doping Mn and Zn in Ba0.5K0.5Fe2As2

TL;DR

This study compares how Mn and Zn doping affect superconductivity in Ba0.5K0.5Fe2As2, revealing Mn's strong pair-breaking effects due to magnetic moments, while Zn's effects are minimal due to different scattering mechanisms.

Contribution

It provides a detailed analysis of how magnetic and non-magnetic impurities differently influence superconductivity in iron-based superconductors.

Findings

Mn doping drastically reduces Tc with strong pair-breaking effects.

Zn doping has negligible impact on Tc and pair-breaking.

Mn induces local magnetic moments that act as pair breakers.

Abstract

Resistivity, Hall effect, magnetoresistance and DC magnetization were measured in Mn and Zn doped Ba$_{0.5}$K$_{0.5}$Fe$_{2}$As$_{2}$ samples. It is found that the Mn-doping can depress the superconducting transition temperature drastically with a rate of $\Delta T_c$/Mn-1% = -4.2 K, while that by Zn-doping is negligible. Detailed analysis reveals that the Mn-doping enhances the residual resistivity ($\rho_0$) significantly, and induces strong local magnetic moments ($\sim$ 2.58 $\mu_B$) which play as pair breakers. While the impurity scattering measured by $\rho_0$ in the Zn-doped samples is much weaker, accompanied by a negligible pair breaking effect. A possible explanation is that the impurity scattering by the Zn impurities are mainly small angle scattering (or small momentum transfer), therefore it cannot break the pairing induced by the interpocket scattering and thus affect the superconducting transition temperature weakly.