Transport Processes in YBa sub 2 Cu sub 3 O sub x /PrBa sub 2 Cu sub 3 O sub x / YBa sub 2 Cu sub 3 O sub x Ramp Type Josephson Junctions

A study of the YBCO/PBCO/YBCO ramp junctions with and without PBCO barrier shows that the Josephson and normal state behaviors of these structures are determined by the thickness of the PBCO barrier and its nature. The boundary resistance and depression of the YBCO superconducting parameters near the interface do not strongly affect the junction characteristic. For thicknesses of 8-20 nm of the PBCO barrier, the Josephson coupling is established through the high resistive barrier and the behavior of the junctions is better described by a SNINS model than by a SNS weak link model. Proximity effect, resonant tunneling, and strong pair breaking mechanisms are discussed to explain the experimental characteristics. Good agreement with the experimental dependence of the I sub c R sub n product on the temperature and on the PBCO barrier thickness was obtained if a strong pair breaking mechanism in the barrier is taken into account.