Local mapping of dissipative vortex motion

TL;DR

This study uses advanced local measurement techniques to investigate vortex dissipation in a superconductor under alternating magnetic fields, revealing slow microscopic loss mechanisms involving thermally activated vortex hopping.

Contribution

It provides the first local, high-resolution analysis of vortex dissipation dynamics under AC magnetic fields in superconductors.

Findings

Vortices exhibit significant phase lag indicating dissipation.

Dissipation occurs at timescales comparable to the driving period.

Thermally activated vortex hopping mediates slow loss mechanisms.

Abstract

We explore, with unprecedented single vortex resolution, the dissipation and motion of vortices in a superconducting ribbon under the influence of an external alternating magnetic field. This is achieved by combing the phase sensitive character of ac-susceptibility, allowing to distinguish between the inductive-and dissipative response, with the local power of scanning Hall probe microscopy. Whereas the induced reversible screening currents contribute only inductively, the vortices do leave a fingerprint in the out-of-phase component. The observed large phase-lag demonstrates the dissipation of vortices at timescales comparable to the period of the driving force (i.e. 13 ms). These results indicate the presence of slow microscopic loss mechanisms mediated by thermally activated hopping transport of vortices between metastable states.