Chaotic Noise Observed in a Resistively Shunted Self-Resonant Josephson Tunnel Junction

The current-voltage characteristics of Josephson tunnel junctions shunted by a resistance with a substantial self-inductance exhibit stable negative-resistance regions. Very large increases in the low-frequency voltage noise with temperatures of ${10}^6$ K or more observed near these regions arise from switching between subharmonic modes. Moderate increases in the noise, with temperatures of about ${10}^3$ K, arise from chaotic behavior. These results are substantiated by analog and digital simulations.