High T c superconductor-normal-superconductor Josephson junctions using CaRuO3 as the metallic barrier

Abstract

Josephson junctions of the SNS type have been fabricated in the edge and trilayer junction geometries using YBa₂Cu₃O_7−δ/CaRuO₃/YBa₂Cu₃O_7−δ. The conducting oxide CaRuO₃ was chosen because it grows epitaxially on YBa₂Cu₃O_7−δ and its resistivity shows metallic behavior. Current‐voltage characteristics display behavior with significant deviations from the resistivity shunted junction model. The dependence of critical currents and junction resistances on the CaRuO₃ thickness suggest that the interface resistance between YBa₂Cu₃O_7−δ and CaRuO₃ plays an important role in determining the critical parameters of the junctions. A dc SQUID functioning at 77 K has been demonstrated with this type of junction.