Suppression of critical temperature in Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ with point defects introduced by proton irradiation

TL;DR

This study investigates how 3 MeV proton irradiation introduces point defects in Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ crystals, leading to suppression of the superconducting critical temperature and increased residual resistivity, with implications for understanding scattering mechanisms.

Contribution

It provides new insights into the effects of proton-induced point defects on superconductivity in iron-based superconductors, highlighting nonmagnetic scattering behavior and challenging existing pairing models.

Findings

$T_c$ decreases monotonically with irradiation dose

Residual resistivity increases with irradiation dose

Defects act as nonmagnetic scattering centers

Abstract

We report the effect of 3 MeV proton irradiation on the suppression of the critical temperature $T_{c}$ in Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ single crystals at under-, optimal-, and over-doping levels. We find that $T_{c}$ decreases and residual resistivity increases monotonically with increasing dose. We also find no upturn in low-temperature resistivity in contrast with the $\yen alpha$-particle irradiated NdFeAs(O,F), which suggests that defects induced by the proton irradiation behave as nonmagnetic scattering centers. The critical scattering rate for all samples estimated by three different ways is much higher than that expected in $s_{\yen pm}$-pairing scenario based on inter-band scattering due to antiferro-magnetic spin fluctuation.