Numerical Demonstration of Relaxation Oscillation in a Resistive Superconducting Quantum Interference Device With Two Nonhysteretic Josephson Junctions

The author numerically demonstrates that a resistive superconducting quantum interference device (RSQUID) with two nonhysteretic Josephson junctions works as a relaxation oscillator. Sequential switching of the Josephson junctions transfers positive and negative flux quanta in the RSQUID loop one by one. Differently from a conventional two-junction superconducting quantum interference device, the dissipative RSQUID loop does not maintain the quantized flux, and hence, finite flux can be accumulated in the RSQUID loop during sequential switching of the Josephson junctions. When the accumulated flux reaches a critical value, the corresponding loop current prevents subsequent junction switching. That is, the oscillation stops. After the loop current decays, sequential switching of the junctions resumes. In addition to the waveforms of relaxation oscillation, dependence of relaxation oscillation on device parameters is presented.