Mesoscopic superconducting disks

TL;DR

This paper investigates the behavior of mesoscopic type I superconducting disks under magnetic fields using Ginzburg-Landau equations, revealing phase transitions, vortex states, and metastability, with analysis aligning theory with experimental data.

Contribution

It introduces a detailed theoretical analysis of finite-sized superconducting disks, including effects of thickness and magnetic field, and connects these to experimental observations.

Findings

Identification of first and second order phase transitions.

Discovery of multiple vortex states depending on disk size.

Quantitative agreement with experimental magnetization data.

Abstract

Using the non-linear Ginzburg-Landau (GL) eqs. type I superconducting disks of finite radius ($R$) and thickness ($d$) are studied in a perpendicular magnetic field. Depending on $R$ and $d$, first or second order phase transitions are found for the normal to superconducting state. For sufficiently large $R$ several transitions in the superconducting phase are found corresponding to different angular momentum giant vortex states. In increasing magnetic field the superconductor is in its ground state, while in field down sweep it is possible to drive the system into metastable states. We also present a quantitative analysis of the relation between the detector output and the sample magnetization. The latter, and the incorporation of the finite thickness of the disks, are essential in order to obtain quantitative agreement with experiment.