Detection of discretized single-shell penetration in mesoscopic vortex matter

TL;DR

This study examines how vortices enter mesoscopic superconducting disks, revealing that vortex entry occurs in discrete shells that shape like the sample edge, as shown by high-resolution magnetometry data.

Contribution

It introduces a geometrical analysis and experimental evidence demonstrating discretized vortex shell entry in mesoscopic superconductors, a novel insight into vortex matter behavior.

Findings

Oscillations in transmittivity linked to vortex shell entry

Peaks in third-harmonics magnetic signal diminish with increasing vortex density

Vortex shells mimic the sample edge shape

Abstract

We investigated configurational changes in mesoscopic vortex matter with less than thousand vortices during flux penetration in freestanding 50 $\mu$m diameter disks of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8 +\delta}$. High-resolution AC and DC local magnetometry data reveal oscillations in the transmittivity echoed in peaks in the third-harmonics magnetic signal fainting on increasing vortex density. By means of extra experimental evidence and a simple geometrical analysis we show that these features fingerprint the discretized entrance of single-shells of vortices having a shape that mimics the sample edge.