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

الأصل · EN

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 Tc, the flux-noise power spectrum S(ω) is white up to a temperature dependent cross-over frequency ωξ(T). We identify ωξ 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/ω dependence.