Imaging of super-fast dynamics and flow instabilities of superconducting vortices

TL;DR

This paper visualizes and analyzes the behavior of superconducting vortices moving at ultrafast speeds, revealing new vortex channel formations and transitions crucial for understanding high-current superconductor physics.

Contribution

It introduces nanoscale imaging of super-fast vortex dynamics and predicts vortex metamorphosis at high velocities, advancing knowledge of superconductor behavior under extreme conditions.

Findings

Vortices penetrate at tens of GHz rates and move up to tens of km/s.

Formation of mesoscopic vortex channels with bifurcations observed.

Predicted transformation of vortices into mixed types at higher velocities.

Abstract

Quantized magnetic vortices driven by electric current determine key electromagnetic properties of superconductors. While the dynamic behavior of slow vortices has been thoroughly investigated, the physics of ultrafast vortices under strong currents remains largely unexplored. Here we use a nanoscale scanning superconducting quantum interference device to image vortices penetrating into a superconducting Pb film at rates of tens of GHz and moving with velocities up to tens of km/s, which are not only much larger than the speed of sound but also exceed the pair-breaking speed limit of superconducting condensate. These experiments reveal formation of mesoscopic vortex channels which undergo cascades of bifurcations as the current and magnetic field increase. Our numerical simulations predict metamorphosis of fast Abrikosov vortices into mixed Abrikosov-Josephson vortices at even higher velocities. This work offers an insight into the fundamental physics of dynamic vortex states of superconductors at high current densities, crucial for many applications.