Low-frequency boundary of the strongly chaotic regime of an rf-driven Josephson junction

The I-V curves of rf-driven underdamped Josephson junctions have been studied in detail both experimentally and numerically. Very large negatively going tails on top of Shapiro steps in the intermediate-dc-current range and smaller wiggling distortions in the lower-dc-current range are observed for rf frequencies obeying 0.2/RC0.4/RC. It is shown that this range is along the low-frequency boundary of the strongly chaotic regime. A physical description is presented to explain successfully the complete I-V curves and the origin of chaos. © 1985 The American Physical Society.