Metastability in a nanobridge-based hysteretic dc SQUID embedded in a superconducting microwave resonator

We study the metastable response of a highly hysteretic dc superconducting quantum interference device (SQUID) made of a niobium loop interrupted by two nanobridges. We excite the SQUID with an alternating current and with direct magnetic flux, and find different stability zones forming diamond-like structures in the measured voltage across the SQUID. When such a SQUID is embedded in a transmission line resonator, similar diamond structures are observed in the reflection pattern of the resonator. We calculate the dc-SQUID stability diagram in the plane of the exciting control parameters, both analytically and numerically. In addition, we obtain numerical simulations of the SQUID equations of motion, taking into account temperature variations and nonsinusoidal current-phase relation of the nanobridges. Good agreement is found between experimental and theoretical results.