YBa2Cu3Ox/PrBa2Cu3Ox/YBa2Cu3Ox Josephson ramp junctions

Abstract

A detailed study of the fabrication process, current voltage (I‐V) characteristics, and Josephson and normal‐state properties of the YBa2Cu3O x (YBCO)/PrBa2Cu3O x (PBCO)/YBCO ramp junctions is presented. The I‐Vcharacteristics can be well described by the resistively shunted junction model. It was found that the critical currentI c and the normal‐state conductance 1/R n scale linearly with the junction area, whereas I c , the excess current I ex, and I cR n products decrease with increasing barrier thickness. These junctions with cross‐sectional area A have a good controllability, low capacitance, and high values of I cR n and R nA products. The coherence length ξ n of the PBCO barrier is estimated to be between 5 and 8 nm. As unambiguous evidence of the Josephson behavior, the microwave response as a function of the microwave power as well as the modulations of critical currentI c (H) with applied magnetic field are shown. A modulation depth of more than 95% has been observed. Small proximity effect parameters and junctioncapacitance (C/A∼10−7 F/cm2) show an advantage of these junctions for many applications.