Electrical Characteristics of HoBa2Cu3O7-x-La1.5Ba1.5Cu3O7-y-HoBa2Cu3O7-x Junctions with Planar-Type Structures

Abstract
A HoBa2Cu3O7-x -La1.5Ba1.5Cu3O7-y -HoBa2Cu3O7-x junction having a planar structure is fabricated and its electrical characteristics are investigated. The planar junction is formed by sectioning a HoBa2Cu3O7-x layer into two superconducting electrodes keeping a submicrometer between them. Supercurrent is detected for the junction with an electrode spacing smaller than 0.4 µm. Critical current is exponentially dependent on electrode spacing. Superconducting decay length for the La1.5Ba1.5Cu3O7-y layer is 65 nm and is almost independent of temperature up to 70 K. This extraordinary long decay length and anomalous superconducting characteristics are not shown to be explained by the conventional proximity theory, and phenomenologically outlined.