Direct observation of stress accumulation and relaxation in small bundles of superconducting vortices in tungsten thin-films

TL;DR

This study uses STM/S at 100 mK to observe how small bundles of superconducting vortices in tungsten thin-films accumulate and relax stress through continuous deformations and sudden avalanches.

Contribution

It provides direct, real-time visualization of stress dynamics in vortex bundles, revealing the mechanisms of stress accumulation and release in superconducting materials.

Findings

Vortex bundles exhibit directed net motion.

Continuous vortex arrangement changes indicate stress buildup.

Large re-arrangements release accumulated stress.

Abstract

We study the behavior of bundles of superconducting vortices when increasing the magnetic field using scanning tunneling microscopy and spectroscopy (STM/S) at 100 mK. Pinning centers are given by features on the surface corrugation. We find strong net vortex motion in a bundle towards a well defined direction. We observe continuos changes of the vortex arrangements, and identify small displacements, which stress and deform the vortex bundle, separated by larger re-arrangements or avalanches, which release accumulated stress.