Guided nucleation of superconductivity on a graded magnetic substrate

TL;DR

This study demonstrates controlled spatial nucleation of superconductivity on a graded magnetic substrate, showing how vortex-antivortex molecules influence local superconductivity and enhance critical temperature.

Contribution

It introduces a method to control superconductivity nucleation using a graded array of ferromagnetic dots, revealing new ways to manipulate superconducting properties.

Findings

Gradient of antivortex density controls local nucleation

Enhanced critical temperature due to magnetic field and antivortex compensation

Vortex-antivortex molecules induced by ferromagnetic dots

Abstract

We demonstrate the controlled spatial nucleation of superconductivity in a thin film deposited on periodic arrays of ferromagnetic dots with gradually increasing diameter. The perpendicular magnetization of the dots induces vortex-antivortex molecules in the sample, with the number of (anti)vortices increasing with magnet size. The resulting gradient of antivortex density between the dots predetermines local nucleation of superconductivity in the sample as a function of the applied external field and temperature. In addition, the compensation between the applied magnetic field and the antivortices results in an unprecedented enhancement of the critical temperature.