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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