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

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 $f<f_ξ$ and scales as $1/f$ for $f>f_ξ$. Here $f_ξ\proptoξ^{-z}$, where $ξ$ is the correlation length and $z$ is the dynamic exponent. Moreover, when all frequencies are scaled by $f_ξ$, data for different temperatures and frequencies collapse on to a single curve. In addition, we have extracted the dynamic exponent $z$ and found $z=1.98\pm0.03$.