Defect controlled vortex generation in current-carrying narrow superconducting strips

TL;DR

This study experimentally investigates how a single circular hole affects the critical current in narrow superconducting strips, revealing nonmonotonous behavior and mechanisms involving vortex entry and vortex-antivortex pairs.

Contribution

It demonstrates the impact of hole position and size on critical current and distinguishes vortex entry mechanisms through magnetic field dependence.

Findings

Critical current depends nonmonotonously on hole position.

Weak dependence of critical current on hole radius for certain size ranges.

Different vortex destruction mechanisms are identified based on magnetic field response.

Abstract

We experimentally study effect of single circular hole on the critical current $I_c$ of narrow superconducting strip with width $W$ much smaller than Pearl penetration depth $\Lambda$. We found nonmonotonous dependence of $I_c$ on the location of a hole across the strip and a weak dependence of $I_c$ on radius of hole has been found in case of hole with $\xi \ll R \ll W$ ($\xi$ is a superconducting coherence length) which is placed in the center of strip. The observed effects are caused by competition of two mechanisms of destruction of superconductivity - the entrance of vortex via edge of the strip and the nucleation of the vortex-antivortex pair near the hole. The mechanisms are clearly distinguishable by difference in dependence of $I_c$ on weak magnetic field.