Superconductors that do not expel magnetic flux

TL;DR

This paper introduces a novel ultrathin superconducting bilayer that forms a coreless fractional vortex, altering magnetic flux behavior and proposing a practical device design for this phenomenon.

Contribution

It presents the concept of a coreless fractional vortex in a bilayer superconductor with a hole, a new magnetic flux configuration not previously demonstrated.

Findings

Formation of a coreless fractional vortex in a bilayer superconductor.

Magnetic flux density profile becomes similar to a cr0me caramel.

Disappearance of the normal core and flux quantization breaking.

Abstract

An ultrathin superconducting bilayer creates a coreless fractional vortex when only the second layer has a hole. The quantization is broken by the hole, and the normal core disappears. The magnetic flux is no longer confined near the normal core, and its density profile around the hole becomes similar to that of a cr\`eme caramel; the divergence of the magnetic flux density is truncated around the center. We propose basic design of a practical device to realize a coreless fractional vortex.