Vortex crossing and trapping in doubly connected mesoscopic loops of a single-crystal type II superconductor

TL;DR

This study combines numerical and experimental approaches to demonstrate vortex crossing and trapping in mesoscopic NbSe₂ superconducting loops, revealing phase shifts in magnetoresistance oscillations and opening pathways for vortex manipulation in future technologies.

Contribution

It provides the first experimental demonstration of vortex crossing and trapping in mesoscopic superconducting loops with controlled vortex manipulation.

Findings

Vortex trapping causes phase shifts in magnetoresistance oscillations.

Vortex crossing can be directed at constrictions in the loop.

Controlled vortex manipulation is feasible in NbSe₂ devices.

Abstract

Numerical calculations on a mesoscopic ring of a type II superconductor in the London limit suggest that an Abrikosov vortex can be trapped in such a structure above a critical magnetic field and generate a phase shift in the magnetoresistance oscillations. We prepared submicron-sized superconducting loops of single-crystal, type II superconductor NbSe$_2$ and measured magnetoresistance oscillations resulting from vortices crossing the loops. The free energy barrier for vortex crossing determines the crossing rate and is periodically modulated by the external magnetic flux threading the loop. We demonstrated experimentally that the crossing of vortices can be directed at a pair of constrictions in the loop, leading to more pronounced magnetoresistance oscillations than those in a uniform ring. The vortex trapping in both a simple ring and a ring featuring two constrictions was found to result in a phase shift in the magnetoresistance oscillations as predicted in the numerical calculations. The controlled crossing and trapping of vortices demonstrated in our NbSe$_2$ devices provide a starting point for the manipulation of individual Abrikosov vortices, which is useful for future technologies.