Vortex kinks in superconducting films with periodically modulated thickness

TL;DR

This study investigates vortex behavior in superconducting Nb films with periodic thickness variations, revealing how vortex flow regimes and discommensurations influence magnetoresistance at specific matching fields.

Contribution

It introduces experimental and numerical analysis of vortex dynamics in modulated superconducting films, highlighting the role of vortex kinks and flow regimes in magnetoresistance.

Findings

Magnetoresistance exhibits piecewise linear segments with slope changes at matching fields.

Vortex flow regimes are linked to the propagation of discommensurations or kinks.

Numerical simulations confirm the association between linear segments and vortex dynamics.

Abstract

We report magnetoresistance measurements through Nb films having a periodic thickness modulation. The cylinder shaped large-thickness regions of the sample, which form a square lattice, act as repulsive centers for the superconducting vortices. For low driving currents along one of the axes of the square lattice, the resistivity $\rho$ increases monotonously with increasing magnetic field $B$ and the $\rho$--$B$ characteristics are approximately piecewise linear. The linear $\rho$ vs $B$ segments change their slope at matching fields where the number of vortices is an integer or a half integer times the number of protruding cylinders in the sample. Numerical simulations allow us to associate the different segments of linear magnetoresistance to different vortex-flow regimes, some of which are dominated by the propagation of discommensurations (kinks).