Superconducting Wigner Vortex Molecule near a Magnetic Disk

TL;DR

This paper explores the complex vortex structures in a superconducting thin film influenced by a ferromagnetic disk, revealing stable antivortex shells, phase diagrams, and vortex-antivortex transitions within the Ginzburg-Landau framework.

Contribution

It introduces a detailed analysis of vortex-antivortex configurations and phase transitions in superconductor-ferromagnet hybrid systems using non-linear GL theory.

Findings

Antivortices form shells around vortex cores with size-magnetization dependent 'magic numbers'

Constructed an equilibrium vortex phase diagram for the system

Vortex phase transitions involve vortex-antivortex pair creation at the disk edge

Abstract

Within the non-linear Ginzburg-Landau (GL) theory, we investigate the vortex structure in a superconducting thin film with a ferromagnetic disk on top of it. Antivortices are stabilized in shells around a central core of vortices (or a giant-vortex) with size-magnetization controlled ``magic numbers''. An equilibrium vortex phase diagram is constructed. The transition between the different vortex phases occurs through the creation of a vortex-antivortex pair under the magnetic disk edge.