Evidence for a vortex-glass transition in superconducting Ba(Fe$_{0.9}$Co$_{0.1}$)$_{2}$As$_{2}$

TL;DR

This study provides evidence for a vortex-glass phase transition in high-quality Ba(Fe$_{0.9}$Co$_{0.1}$)$_{2}$As$_{2}$ superconductors, revealing weak quenched disorder effects and dynamic scaling behavior near optimal doping.

Contribution

It demonstrates the presence of a vortex-glass transition in Ba(Fe$_{0.9}$Co$_{0.1}$)$_{2}$As$_{2}$ and characterizes the weak impact of chemical disorder on vortex dynamics.

Findings

Vortex-glass phase transition observed near optimal doping.

Dissipative ac susceptibility fits Havriliak-Negami relaxation model.

Weaker quenched disorder effects compared to cuprate superconductors.

Abstract

Measurements of magneto-resistivity and magnetic susceptibility were performed on single crystals of superconducting Ba(Fe$_{0.9}$Co$_{0.1}$)$_{2}$As$_{2}$ close to the conditions of optimal doping. The high quality of the investigated samples allows us to reveal a dynamic scaling behaviour associated with a vortex-glass phase transition in the limit of weak degree of quenched disorder. Accordingly, the dissipative component of the ac susceptibility is well reproduced within the framework of Havriliak-Negami relaxation, assuming a critical power-law divergence for the characteristic correlation time $\tau$ of the vortex dynamics. Remarkably, the random disorder introduced by the Fe$_{1-x}$Co$_{x}$ chemical substitution is found to act on the vortices as a much weaker quenched disorder than previously reported for cuprate superconductors such as, e.g., Y$_{1-x}$Pr$_{x}$Ba$_{2}$Cu$_{3}$O$_{7-\delta}$.