Vortex dynamics in superconducting fractal networks

We report experiments measuring the ac response of a Sierpinski Gasket (SG) of Al wires to a weak driving ac field, as a function of dc magnetic field and driving frequency. Genuine fractal behavior becomes particularly manifest in the network's ac magnetoconductance, where a very rich fine structure reflecting flux quantization phenomena related to the multiconnected self-similar geometry of the gasket is observed. The analysis of the frequency dependence of the fine structure suggests that thermally activated fluctuations have to be taken into account in order to explain the dynamical properties of the system. (orig.)