Ultra-fast vortex motion in a direct-write Nb-C superconductor

O V Dobrovolskiy,O V Dobrovolskiy,R Sachser,A V Chumak,M Yu Mikhailov,D Yu Vodolazov,D Yu Vodolazov,M Huth,V M Bevz,F Porrati

doi:10.1038/s41467-020-16987-y

Abstract

The ultra-fast dynamics of superconducting vortices harbors rich physics generic to nonequilibrium collective systems. The phenomenon of flux-flow instability (FFI), however, prevents its exploration and sets practical limits for the use of vortices in various applications. To suppress the FFI, a superconductor should exhibit a rarely achieved combination of properties: weak volume pinning, close-to-depairing critical current, and fast heat removal from heated electrons. Here, we demonstrate experimentally ultra-fast vortex motion at velocities of 10–15 km s−1 in a directly written Nb-C superconductor with a close-to-perfect edge barrier. The spatial evolution of the FFI is described using the edge-controlled FFI model, implying a chain of FFI nucleation points along the sample edge and their development into self-organized Josephson-like junctions (vortex rivers). In addition, our results offer insights into the applicability of widely used FFI models and suggest Nb-C to be a good candidate material for fast single-photon detectors.

Highlights

The ultra-fast dynamics of superconducting vortices harbors rich physics generic to nonequilibrium collective systems
We study the vortex dynamics in a direct-write Nb-C superconducting microstrip fabricated by FIBID32
When the electric field induced by vortex motion raises the quasiparticle energy above the potential barrier associated with the order parameter around the vortex core, quasiparticles leave it and the core shrinks

Summary

Introduction

The ultra-fast dynamics of superconducting vortices harbors rich physics generic to nonequilibrium collective systems. The phenomenon of flux-flow instability (FFI), prevents its exploration and sets practical limits for the use of vortices in various applications. Fast-moving vortices are known to lead to a quench of the low-dissipative state at I* ≪ Idep as a consequence of the flux-flow instability (FFI) associated with the escape of quasiparticles (normal electrons) from the vortex cores[20,21]. While short τε is inherent to disordered superconducting systems[22,23], few of them have Ic ≲ Idep in conjunction with weak volume pinning needed to maintain long-range order in the fast-moving vortex lattice. Variation in the local pinning forces induced by uncorrelated disorder (volume pinning) leads to a broader distribution of v and thereby prevents the exploration of vortex matter at high velocities[24,25,26,27]

Methods

Results

Conclusion