Heteroepitaxial YBa/sub 2/Cu/sub 3/O/sub 7-x/-PrBa/sub 2/Cu/sub 3/O/sub 7-x/-YBa/sub 2/Cu/sub 3/O/sub 7-x/ weak links grown by laser deposition

The authors have developed a controllable HTSC (high-temperature superconductor) weak-link fabrication process for producing weak links from the high-temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO), using PrBa/sub 2/Cu/sub 3/O/sub 7-x/ (PBCO) as a lattice-matched semiconducting barrier layer. The devices obtained show current-voltage characteristics similar to those observed for low-temperature superconductor/normal-metal/superconductor (SNS) devices. The authors found good scaling of the critical currents I/sub c/ with area, A, and scaling of the resistances R/sub j/ with 1/A; the typical values of the I/sub c/R/sub j/ product of 3.5 mV are consistent with traditional SNS behavior. The authors observed Shapiro steps in response to 100-GHz millimeter-wave radiation and oscillation of the DC supercurrent in a transverse magnetic field, thus demonstrating that both the AC and DC Josephson effects occur in these devices.