Dynamic Scaling of Magnetic Flux Noise Near the KTB Transition in Overdamped Josephson Junction Arrays

TL;DR

This study measures magnetic flux noise near the Kosterlitz-Thouless transition in overdamped Josephson junction arrays, revealing a universal scaling behavior and determining the dynamic exponent with high precision.

Contribution

It provides the first detailed experimental analysis of flux noise scaling and dynamic exponent near the KTB transition in Josephson junction arrays.

Findings

Flux noise is white below a characteristic frequency and scales as 1/f above it.

The characteristic frequency scales with correlation length as f_xi ∝ ξ^{-z}.

The dynamic exponent z is measured to be approximately 2.

Abstract

We have used a dc Superconducting QUantum Interference Device to measure the magnetic flux noise generated by the equilibrium vortex density fluctuations associated with the Kosterlitz-Thouless-Berezinskii (KTB) transition in an overdamped Josephson junction array. At temperatures slightly above the KTB transition temperature, the noise is white for $f<f_\xi$ and scales as $1/f$ for $f>f_\xi$. Here $f_\xi\propto\xi^{-z}$, where $\xi$ is the correlation length and $z$ is the dynamic exponent. Moreover, when all frequencies are scaled by $f_\xi$, data for different temperatures and frequencies collapse on to a single curve. In addition, we have extracted the dynamic exponent $z$ and found $z=1.98\pm0.03$.