Pressure effects on the electron-doped high Tc superconductor BaFe(2-x)Co(x)As(2)

TL;DR

This study investigates how pressure influences superconductivity in electron-doped BaFe(2-x)Co(x)As(2), revealing that pressure can significantly enhance Tc in underdoped samples by suppressing magnetic order.

Contribution

It provides systematic transport measurements under pressure, demonstrating the interplay between electron doping, pressure, and magnetic instability in iron-based superconductors.

Findings

Pressure suppresses magnetic instability in underdoped samples.

Tc nearly doubles in underdoped samples under pressure.

Optimally doped samples show minimal Tc change with pressure.

Abstract

Application of pressures or electron-doping through Co substitution into Fe sites transforms the itinerant antiferromagnet BaFe(2)As(2) into a superconductor with the Tc exceeding 20K. We carried out systematic transport measurements of BaFe(2-x)Co(x)As(2) superconductors in pressures up to 2.5GPa, and elucidate the interplay between the effects of electron-doping and pressures. For the underdoped sample with nominal composition x = 0.08, application of pressure strongly suppresses a magnetic instability while enhancing Tc by nearly a factor of two from 11K to 21K. In contrast, the optimally doped x=0.20 sample shows very little enhancement of Tc=22K under applied pressure. Our results strongly suggest that the proximity to a magnetic instability is the key to the mechanism of superconductivity in iron-pnictides.