Novel Increase of Superconducting Critical Temperature of an Iron-Superconductor due to Ion Implantation

TL;DR

This study demonstrates a significant increase in the superconducting critical temperature of an iron-based superconductor through ion implantation, attributed to induced compressive strain from inert gas bubbles.

Contribution

It reports the first large Tc enhancement in an iron superconductor caused by ion implantation, expanding understanding of irradiation effects on superconductivity.

Findings

Tc increased by 8.2 K after Ar ion irradiation

Inert gas implantation creates compressive strain in the crystal lattice

Large Tc enhancement (~49%) observed due to ion-induced lattice effects

Abstract

Energetic ion irradiation usually decreases superconducting critical temperature(Tc), with the few exceptions involving increases up to a few K only. However, our recent 2.5X10^15 Ar/cm2 irradiations by 1.5 MeV Ar6+ enhanced Tc of the single crystal Fe-superconductor Ba(Fe0.943Co0.057)2As2 by 8.2 K from its initial onset Tc of ~16.9 K as measured from the real part of the magnetic susceptibility, matching measurements from the imaginary part, electrical resistivity and magnetization. Ozaki et al. (2016) explained their Tc increase of 0.5 K in FeSe0.5Te0.5 films with the thickness (t) < the irradiating proton range (R), as due to a nanoscale compressive strain developed from radiation damage of the lattice. Here, Ar irradiation with t > R results in an Ar implanted layer in our crystal. Implanted inert gas atoms often agglomerate into high-pressure bubbles to exert a large compressive strain on the lattice. We suggest that this additional compressive strain could be the reason for such a large (~49%) Tc increase.