Overscreening Diamagnetism in Cylindrical Superconductor-Normal Metal-Heterostructures

TL;DR

This paper investigates the enhanced diamagnetic response in cylindrical superconductor-normal metal heterostructures, revealing stronger overscreening effects compared to planar geometries due to spatial oscillations of the magnetic field.

Contribution

It provides a detailed analysis of the magnetic susceptibility in cylindrical geometries, highlighting the impact of curvature and spatial oscillations on overscreening phenomena.

Findings

Stronger overscreening in cylinders when radius is comparable to normal layer thickness

Increased diamagnetism compared to planar structures for large radii

Spatial oscillations of magnetic field explain the enhanced effects

Abstract

We study the linear diamagnetic response of a superconducting cylinder coated by a normal-metal layer due to the proximity effect using the clean limit quasiclassical Eilenberger equations. We compare the results for the susceptibility with those for a planar geometry. Interestingly, for $R\sim d$ the cylinder exhibits a stronger overscreening of the magnetic field, i.e., at the interface to the superconductor it can be less than (-1/2) of the applied field. Even for $R\gg d$, the diamagnetism can be increased as compared to the planar case, viz. the magnetic susceptibility $4\pi\chi$ becomes smaller than -3/4. This behaviour can be explained by an intriguing spatial oscillation of the magnetic field in the normal layer.