Resonances in superconducting quantum interference devices—SQUID’s

Resonances in asymmetric two junction SQUID’s are analyzed. The distinction between current-controlled and voltage-controlled cases is found to be crucial to the full understanding of the device dynamics. In the current-controlled case, three modes of oscillation are predicted at frequencies [(L1+L2)C1]−1/2, [(L1+L2)C2]−1/2, and [(L1+L2)C1+C2/(C1+C2)]−1/2, and confirmed experimentally. In the voltage-controlled case only two modes are predicted at frequencies (L1C1)−1/2 and (L2C2)−1/2, which in practice are difficult to observe. We show that such a distinction leads to a better interpretation of experimental observations.