Narrow-band noise due to the moving vortex lattice in superconducting niobium

TL;DR

This study investigates voltage noise caused by vortex motion in superconducting niobium, revealing narrow-band noise with a frequency linked to vortex velocity, indicating large-scale temporal coherence even near depinning and peak effect regions.

Contribution

It provides the first detailed measurement of narrow-band noise in niobium, demonstrating large-scale temporal coherence of vortex motion across different regimes.

Findings

Narrow band noise frequency scales with vortex velocity.

NBN persists near depinning and peak effect, indicating long-range correlations.

Temporal coherence exists over large scales in vortex flow.

Abstract

We report measurements of voltage noise due to vortex motion in Niobium, a conventional low-Tc superconductor. A coherent oscillation leading to narrow band noise (NBN) is evidenced. Its characteristic frequency is a linear function of the overcritical transport current in the flux-flow regime, and hence scales as the main velocity of the vortex flow. The associated length scale is not the intervortex distance but the width of the sample, indicating temporal coherence at a large scale. NBN is also observed in the non linear part of the V(I) at the onset of depinning, in apparent disagreement with a stochastic creep motion of flux bundles. NBN exists in the peak effect region, showing that long range temporal correlations are preserved in this regime.