Oscillatory dynamics of a superconductor vortex lattice in high amplitude ac magnetic fields

TL;DR

This study investigates how high amplitude ac magnetic fields affect the mobility and order of vortex lattices in superconductors, revealing that large symmetric oscillations tend to reduce vortex mobility and promote plastic flow.

Contribution

It provides experimental evidence that large symmetric ac fields decrease vortex lattice mobility and induce plastic flow, confirming recent simulation predictions.

Findings

Large symmetric ac fields reduce vortex lattice mobility.

Vortex lattices evolve towards less mobile states under high amplitude oscillations.

Symmetric fields promote plastic flow in vortex lattices.

Abstract

In this work we study by ac susceptibility measurements the evolution of the solid vortex lattice mobility under oscillating forces. Previous work had already shown that in YBCO single crystals, below the melting transition, a temporarily symmetric magnetic ac field (e.g. sinusoidal, square, triangular) can heal the vortex lattice (VL) and increase its mobility, but a temporarily asymmetric one (e.g. sawtooth) of the same amplitude can tear the lattice into a more pinned disordered state. In this work we present evidence that the mobility of the VL is reduced for large vortex displacements, in agreement with predictions of recent simulations. We show that with large symmetric oscillating fields both an initially ordered or an initially disordered VL configuration evolve towards a less mobile lattice, supporting the scenario of plastic flow.