Glassy Transition in the Vortex Lattice of Ba(Fe0.93Rh0.07)2As2 superconductor, probed by NMR and ac-susceptibility

TL;DR

This study investigates the vortex glass transition in Ba(Fe0.93Rh0.07)2As2 superconductor using NMR and ac-susceptibility, revealing universal vortex dynamics and a phase diagram consistent with glassy behavior.

Contribution

It provides experimental evidence of vortex glass transition in an iron-based superconductor using NMR and ac-susceptibility, and characterizes the vortex dynamics and phase diagram.

Findings

Vortex dynamics show a crossover consistent with a vortex glass transition.

Correlation times follow the Vogel-Fulcher law, not Arrhenius.

Glass freezing temperatures align with the de Almeida-Thouless line.

Abstract

By using Nuclear Magnetic Resonance and ac-susceptibility, the characteristic correlation times for the vortex dynamics, in an iron-based superconductor, have been derived. Upon cooling, the vortex dynamics displays a crossover consistent with a vortex glass transition. The correlation times, in the fast motions regime, merge onto a universal curve which is fit by the Vogel-Fulcher law, rather than by an Arrhenius law. Moreover, the pinning barrier shows a weak dependence on the magnetic field which can be heuristically justified within a fragile glass scenario. In addition, the glass freezing temperatures obtained by the two techniques merge onto the de Almeida-Thouless line. Finally the phase diagram for the mixed phase has been derived.