Transport characteristics of ramp-type YBa2Cu3O7-δ/PrBa2Cu3O7-y/YBa2Cu3O7-δ Josephson junctions

Abstract

The transport behaviors of YBa2Cu3O7-δ/PrBa2Cu3O7-y/YBa2Cu3O7-δ junctions with barrier thickness ranging from 6 to 30 nm were studied. In these junctions, the existence of a proximity layer was confirmed by the appearence of a temperature-dependent coherence length. The structure of the junctions changed from SNS to SNINS with increasing barrier thickness. It was found that the quasiparticles transport through a thin barrier by metallic conduction and through a thick barrier by tunneling conduction. In junctions with a moderate barrier thickness, we found a subgaplike feature in the conductance-voltage curves, which could be related to multiple Andreev reflection in a SNcNS Josephson junction. For junctions with a thick barrier, the dependence of conductance on temperature could be well fitted by the T4/3 law. This suggested that the quasiparticles transport across a thick PrBa2Cu3O7-y barrier layer via two localized states in an inelastic tunneling process.