Mutual phase locking in systems of high-Tc superconductor-normal metal-superconductor junctions

摘要

Abstract: We have investigated the interaction between high critical temperature (high-T$-c$/) superconductor-normal metal- superconductor step-edge junctions coupled through a non- superconducting feedback loop. We have characterized the strength of the interaction as a function of frequency and temperature for both a circuit without a groundplane and an all high-T$-c$/ multilayer circuit incorporating a superconducting ground plane. We observed relative locking strengths (the ratio of the measured locking current I$-L$/ to the junctions average critical current I$-c$/) as large as I$-L$/I$-c$/$EQ@9% and peak locking frequencies as high as 1.06 THz. The maximum temperature at which locking occurred was 35 K. An analysis of the temperature dependence of the locking current accounting for thermal fluctuations in the context of Johnson noise from resistive elements in the circuit agrees well with our experimental observations. !14