Magnetic Dipoles at Topological Defects in the Meissner State of a Nanostructured Superconductor

TL;DR

This study experimentally demonstrates magnetic dipoles formed by Meissner currents around topological defects in a superconductor, revealing their dependence on local currents and their role in vortex depinning.

Contribution

It provides the first experimental observation of magnetic dipoles at topological defects in a superconductor using scanning Hall probe microscopy.

Findings

Magnetic dipoles are generated at antidots in a superconducting film.

The magnetic dipoles depend on the local Meissner current.

Magnetic dipoles influence vortex depinning behavior.

Abstract

In a magnetic field, superconductivity is manifested by total magnetic field expulsion (Meissner effect) or by the penetration of integer multiples of the flux quantum {\Phi}_0. Here we present experimental results revealing magnetic dipoles formed by Meissner current flowing around artificially introduced topological defects (lattice of antidots). By using scanning Hall probe microscopy, we have detected ordered magnetic dipole lattice generated at spatially periodic antidots in a Pb superconducting film. While the conventional homogeneous Meissner state breaks down, the total magnetic flux of the magnetic dipoles remains quantized and is equal to zero. The observed magnetic dipoles strongly depend on the intensity and direction of the locally flowing Meissner current, making the magnetic dipoles an effective way to monitor the local supercurrent. We have also investigated the first step of the vortex depinning process, where, due to the generation of magnetic dipoles, the pinned Abrikosov vortices are deformed and shifted from their original pinning sites.