UCL Discovery

Abstract

We have fabricated intrinsic Josephson junction arrays in thin films of Tl-Ba-Ca-Cu-O. Such arrays are candidates for applications in the sub-millimeter waveband both by virtue of the large gap energy and due to the existence of inductive and capacitive coupling mechanisms between junctions in the array. Characterization of such junctions is complicated by the fact that the transport properties are dominated by Josephson fluxon flow (for junctions whose dimensions exceed the Josephson penetration depth) and premature switching to the voltage state at bias currents less than the critical current (for junctions whose dimensions are less than the Josephson penetration depth). Here we show that the magnetic-field dependence of the switching current is not Fraunhofer-like, although there is clear minimum corresponding to the point at which a single flux quantum is inserted between the cuprate double-planes. Nevertheless a Fraunhofer-like dependence can be obtained if the critical current is experimentally defined by specifying a low-voltage criterion.

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