The Confinement of Vortices in Nano-Superconducting Devices

TL;DR

This study explores how 3-D vortices behave in nano-superconducting cylinders, revealing that vortex patterns and phase transitions depend on device size, shape, and magnetic field orientation, with significant surface barrier effects.

Contribution

It provides new insights into vortex confinement and phase transition types in nano-superconductors with cylindrical geometry under different magnetic field orientations.

Findings

Vortex patterns depend on device size and magnetic field orientation.

Nano-cylinders can exhibit first or second order phase transitions.

Giant vortex states emerge under longitudinal magnetic fields.

Abstract

We have investigated the confinement of 3-D vortices in specific cases of Type-II ($\kappa = 2$) nano-superconducting devices. The emergent pattern of vortices greatly depends on the orientation of an applied magnetic field (transverse or longitudinal), and the size of the devices (a few coherence lengths $\xi$). Herein, cylindrical geometries are examined. The surface barriers become very significant in these nano-systems, and hence the characteristics of the vortices become highly sensitive to the shape of the system and direction of an applied field. It is observed that nano-cylindrical superconductors, depending on their sizes, can display either first or second order phase transitions, under the influence of a longitudinal field. In the confined geometries, nucleation of a giant vortex state composed of a n-quanta emerges for the longitudinal magnetic field.