Vortex States of a Superconducting Film from a Magnetic Dot Array

TL;DR

This paper uses Ginzburg-Landau theory to explore vortex configurations in superconducting films influenced by magnetic dot arrays, revealing vortex-antivortex pairs and symmetry-breaking states with tunable properties.

Contribution

It introduces novel vortex configurations in superconducting films due to magnetic dot arrays and proposes an experiment to tune vortex-antivortex densities via magnetic fields.

Findings

Vortex-antivortex pairs form with strong magnetic dots.

Vortex configurations can break lattice symmetries.

Vortex-antivortex pair density exhibits broad plateaus with dipole strength.

Abstract

Using Ginzburg-Landau theory, we find novel configurations of vortices in superconducting thin films subject to the magnetic field of a magnetic dot array, with dipole moments oriented perpendicular to the film. Sufficiently strong magnets cause the formation of vortex-antivortex pairs. In most cases, the vortices are confined to dot regions, while the antivortices can form a rich variety of lattice states. We propose an experiment in which the perpendicular component of the dot dipole moments can be tuned using an in-plane magnetic field. We show that in such an experiment the vortex-antivortex pair density shows broad plateaus as a function of the dipole strength. Many of the plateaus correspond to vortex configurations which break dot lattice symmetries. In some of these states, the vortex cores are strongly distorted. Possible experimental consequences are mentioned.