Internal avalanches in a pile of superconducting vortices

TL;DR

This study investigates internal vortex avalanches in a superconducting niobium sample, revealing power-law distributed avalanches and large jumps that influence the system's critical current, using real-time magnetic induction measurements.

Contribution

It provides the first detailed experimental observation of internal vortex avalanches and their statistical properties in a superconductor under varying magnetic fields.

Findings

Avalanche sizes follow a power-law distribution.

Large avalanches occur at low temperatures and fields.

The system lacks a well-defined macroscopic critical current during large avalanches.

Abstract

Using an array of miniature Hall probes, we monitored the spatiotemporal variation of the internal magnetic induction in a superconducting niobium sample during a slow sweep of external magnetic field. We found that a sizable fraction of the increase in the local vortex population occurs in abrupt jumps. The size distribution of these avalanches presents a power-law collapse on a limited range. In contrast, at low temperatures and low fields, huge avalanches with a typical size occur and the system does not display a well-defined macroscopic critical current.