COMPLEX DYNAMICS OF RESISTIVELY AND INDUCTIVELY SHUNTED JOSEPHSON-JUNCTIONS

We have measured Nb-AlOx-Nb Josephson tunnel junctions which have resi stive shunts with different parasitic inductances. Numerical simulatio ns reveal that specific features in the experimental current-voltage ( I-V) characteristics of these devices are de signatures of complex ac behavior. Depending on the inductance of the shunt loop and the capaci tance of the junction, these features may either appear or disappear a s the temperature of the device is increased. Examination of the simul ated voltage waveforms allows us to map regions of the parameter space which exhibit complicated behavior. These regions should be avoided w hen a nearly sinusoidal voltage waveform is desired, as is the case fo r Josephson junction-based oscillators. The agreement of the experimen tal and simulated I-V curves also enables us to accurately determine t he inductance of the shunts and the capacitance of the junctions. (C) 1998 American Institute of Physics. [S0021-8979(98)03714-1].