Synchronous Regimes in YBCO Long Josephson Junctions Fabricated by Preliminary Topology Masks

We present the results of experimental and theoretical study of velocity matching and Shapiro steps of long YBCO Josephson junctions on bicrystal YSZ substrates. YBCO films were fabricated by the magnetron sputtering with modification of the substrate surface by original preliminary topology mask technology. This technology allows to fabricate YBCO structures on YSZ substrate with buffer cerium dioxide CeO
₂
layer where YBCO film sputtering is the final stage of the structure formation. The advantage of this technology is the absence of degrading action on superconducting elements, as occurs during commonly used operations such as etching or ion implantation. In particular, long Josephson junctions with good characteristics have been fabricated by this technology and measured, allowing to achieve critical currents of order 200 mA for 350 um junctions at 6K temperature. The velocity matching steps have been studied at various external magnetic fields and their asymmetry for opposite fields signs has been revealed. The joint effect of velocity matching and Shapiro steps has been studied both experimentally and numerically. The wide variety of subharmonic Shapiro steps has been observed and their dependence on magnetic field and the temperature has been studied.