# Structural Transition Kinetics and Activated Behavior in the Superconducting Vortex Lattice

## TL;DR

This study explores the kinetics of vortex lattice transitions in MgB2 using neutron scattering, revealing activated behavior, aging effects, and a crossover in metastable domain suppression driven by AC magnetic fields.

## Contribution

It introduces a novel understanding of collective vortex behavior, highlighting the role of nucleation and growth of equilibrium domains under AC field influence.

## Key findings

- Activated behavior of vortex lattice transition observed.
- Aging of the vortex lattice correlates with increased activation barrier.
- Crossover from partial to complete suppression of metastable domains.

## Abstract

Using small-angle neutron scattering, we investigated the behavior of a metastable vortex lattice state in MgB2 as it is driven towards equilibrium by an AC magnetic field. This shows an activated behavior, where the AC field amplitude and cycle count are equivalent to, respectively, an effective "temperature" and "time". The activation barrier increases as the metastable state is suppressed, corresponding to an aging of the vortex lattice. Furthermore, we find a cross-over from a partial to a complete suppression of metastable domains depending on the AC field amplitude, which may empirically be described by a single free parameter. This represents a novel kind of collective vortex behavior, most likely governed by the nucleation and growth of equilibrium vortex lattice domains.