Investigation of vortex dynamics in Josephson junction arrays with magnetic flux noise measurements

Abstract

We have measured the magnetic flux noise in a two-dimensional Josephson junction array in nominally zero magnetic field, in the vicinity of the superconducting transition. This transition is of the Berezinski-Kosterlitz-Thouless (BKT) type, driven by the unbinding of thermally excited vortex-antivortex pairs. At temperatures just above the BKT transition temperature $T_c$, the flux-noise power spectrum $S(\omega )$ is white up to a temperature dependent cross-over frequency ${\omega }_{\xi }(T)$. We identify ${\omega }_{\xi }$ with the characteristic time related to the scale at which the cross-over from free vortex response to a response dominated by bound pairs occurs. The signature of free vortices is thus white noise while bound vortex pairs give rise to a $1/\omega$ dependence.

To be published in Physica C (Proceedings of the European Conference in School Format 'Vortex Matter in Superconductors II')

Cited by in corpus (2)

• Vortex dynamics in two-dimensional Josephson junction arrays
• Fluctuation-dissipation theorem and flux noise in overdamped Josephson junction arrays