Transport signatures of fragile-glass dynamics in the melting of the two-dimensional vortex lattice

TL;DR

This study investigates the transport properties of 2D vortex lattices in amorphous MoGe films, revealing fragile-glass dynamics at low fields and a transition to strong-glass behavior at high fields, providing new insights into 2D melting phenomena.

Contribution

It demonstrates the presence of fragile-glass dynamics in 2D vortex systems and elucidates how orientational correlations influence melting and disorder effects.

Findings

Resistivity follows Vogel-Fulcher-Tamman form at low fields.

Suppression of T0(H) leads to standard vortex liquid behavior.

Crossover from fragile to strong-glass behavior with increasing magnetic field.

Abstract

In two-dimensional (2D) systems, the melting from a solid to an isotropic liquid can occur via an intermediate phase that retains orientational order. However, in 2D superconducting vortex lattices, the effect of orientational correlations on transport, and their interplay with disorder remain open questions. Here we study a 2D weakly pinned vortex system in amorphous MoGe films over an extensive range of temperatures ($\bm{T}$) and perpendicular magnetic fields ($\bm{H}$) using linear and nonlinear transport measurements. We find that, at low fields, the resistivity obeys the Vogel-Fulcher-Tamman (VFT) form, $\bm{\rho(T)\propto\exp[-{W}(H)/(T-T_0(H))]}$, characteristic of fragile glasses. As $\bm{H}$ increases, $\bm{T_0(H)}$ is suppressed to zero, and a standard vortex liquid behavior consistent with a $\bm{T=0}$ superconducting transition is observed. Our findings, supported also by simulations, suggest that the presence of orientational correlations gives rise to a heterogeneous dynamics responsible for the VFT behavior. The effects of quenched disorder become dominant at high $\bm{H}$, where a crossover to a strong-glass behavior is observed. This is a new insight into the dynamics of melting in 2D systems with competing orders.