Dimensional crossover and hidden incommensurability in Josephson junction arrays of periodically repeated Sierpinski gaskets

Article

关键词: SUPERCONDUCTING PHASE-BOUNDARY;    FRUSTRATED XY MODELS;    MAGNETIC-FIELD;    TRIANGULAR LATTICE;    VORTEX DYNAMICS;    WIRE NETWORKS;    PERCOLATION;    DISORDER;    TRANSITIONS;    THRESHOLD;   

DOI  :  10.1103/PhysRevB.66.104503

来源: SCIE

【 摘 要 】

We report a study of overdamped Josephson junction arrays with the geometry of periodically repeated Sierpinski gaskets. These model superconductors share essential geometrical features with truly random (percolative) systems. When exposed to a perpendicular magnetic field B, their Euclidian or fractal behavior depends on the relation between the intervortex distance (imposed by B) and the size of a constituent gasket, and was explored with high-resolution measurements of the sample magnetoinductance L(B). In terms of the frustration parameter f expressing (in units of the superconducting flux quantum) the magnetic flux threading an elementary triangular cell of a gasket, the crossover between the two regimes occurs at f(cN)=1/(2x4(N)), where N is the gasket order. In the fractal regime (f>f(cN)) a sequence of equally spaced structures corresponding to the set of states with unit cells not larger than a single gasket is observed at multiples of f(cN), as predicted by theory. The fine structure of L(f) radically changes in the Euclidian regime (f

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