High <i>T</i> <i>c</i> 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 YBa2Cu3O7−δ/CaRuO3/YBa2Cu3O7−δ. The conducting oxide CaRuO3 was chosen because it grows epitaxially on YBa2Cu3O7−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 YBa2Cu3O7−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.