Lorentz force on superconducting vortices near line defects

TL;DR

This paper analyzes the Lorentz force acting on vortices in thin-film superconductors near line defects, combining analytical and numerical methods to improve understanding of vortex pinning and dynamics for superconducting applications.

Contribution

It provides a detailed estimation of Lorentz forces on vortices near line defects using analytical and numerical approaches, enhancing understanding of vortex behavior in defect-engineered superconductors.

Findings

Force on vortices near defects is enhanced compared to homogeneous regions.

Pinning vortices on defects increases force perpendicular to defects.

Vortices between defects experience force enhancement along the defect direction.

Abstract

In type-II superconductors, magnetic flux penetrates in the form of quantized vortices whose dissipative motion, driven by the Lorentz force, can degrade superconductivity. Understanding vortex dynamics in both homogeneous regions and near unavoidable structural defects is crucial for superconducting applications. This study examines a scenario in which a superconducting quantum interference device (SQUID) scans across a thin-film superconductor containing line defects. We first estimate the radial Lorentz force on a vortex in a homogeneous region using both analytical methods and numerical simulations based on the fast Fourier transform algorithm. For a film with a Pearl length of 400 micrometers and a SQUID height of 4 micrometers, we find that the SQUID tip can exert a force of approximately 3 femtonewtons on a vortex. We then evaluate the Lorentz force on vortices near two parallel line defects. Our results show that the Lorentz force is enhanced for vortices pinned on or between line defects. Vortices pinned on the line defects experience force enhancement predominantly perpendicular to the defects, while vortices in between experience enhancement along the defect direction. These findings enable more accurate estimation of Lorentz forces on vortices near line defects in thin-film superconductors and contribute to the broader understanding of vortex pinning and dynamics in defect-engineered superconductors. The methods can be extended to bulk superconductors and generalized to other defect geometries.