Percolation process on the superconducting paths in Y1−xPrxBa2Cu3O7−δ

Abstract

In the compound Y1−xPrxBa2Cu3O7−δ, a two-dimensional site-percolation system of the square lattice is realized with structural elements of Y-sited and Pr-sited crystal unit cells. The diamagnetic behavior at temperatures as low as 4.2 K has revealed that superconductivity is featured by the several characteristic points in the range of Pr concentration (x): the first percolation threshold xpc1=0.41, the second one xpc2=0.59, and virtual thresholds x1=0.44 and x2=0.55. At these points the superconducting path changes in its structure. In the range x2>~x>~x1, the path becomes fragile, largely depending on the magnetic field h(ac). The presence of x2 implies that the isolated Y-sited unit cell is assimilated into the adjacent Pr-sited cells, and so the percolation threshold is shifted from the true one xpc2 to the virtual one x2. If this effect occurs also to the isolated Pr-sited unit cell, then x1 becomes a virtual threshold stemming from xpc1.

Source-reported materials — not catalogue approval

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