Fractal Networks, Braiding Channels, and Voltage Noise in Intermittently Flowing Rivers of Quantized Magnetic Flux

TL;DR

This paper investigates vortex dynamics in fractal channel networks within superconductors, linking microscopic vortex motion to macroscopic voltage noise, revealing universal behavior related to pinning strength.

Contribution

It introduces a detailed analysis of vortex flow through fractal channels and connects microscopic properties to measurable voltage noise spectra, highlighting a universal transition.

Findings

Universal drop in tortuosity and noise power at a critical pinning strength

Vortex motion transitions from braiding to unbraided channels

Correlation between fractal network properties and voltage noise spectrum

Abstract

We analyze the microscopic dynamics of vortex motion through channels that form river-like fractal networks in a variety of superconducting samples, and relate it to macroscopic measurable quantities such as the power spectrum. As a function of pinning strength, we calculate the fractal dimension, tortuosity, and the corresponding voltage noise spectrum. Above a certain pinning strength, a remarkable universal drop in both tortuosity and noise power occurs when the vortex motion changes from shifting braiding channels to unbraided channels. We compare our results with experiments.