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Avalanche-driven fractal flux distributions in NbN superconducting films

I. A. Rudnev·D. V. Shantsev·T. H. Johansen·A. E. Primenko
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Abstract

Flux distributions in thin superconducting NbN films placed in a perpendicular magnetic field have been studied using magneto-optical imaging. Below 5.5 K the flux penetrates in the form of abrupt avalanches resulting in dendritic structures. Magnetization curves in this regime exhibit extremely noisy behavior. Stability is restored both above a threshold temperature T* and applied field H*, where H* is smaller for increasing field than during descent. The dendrite size and morphology are strongly T dependent, and fractal analysis of the first dendrites entering into a virgin film shows that dendrites formed at higher T have larger fractal dimension.

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I. A. Rudnev, D. V. Shantsev, T. H. Johansen, A. E. Primenko. 2004-11-18. Avalanche-driven fractal flux distributions in NbN superconducting films. https://doi.org/10.1063/1.1992673

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