Tunable mechanically-induced hysteresis in suspended Josephson junctions

Abstract

The coupling of superconducting systems to mechanical resonators is an emerging field, with wide reaching implications including high precision sensing and metrology. Experimental signatures of this coupling have so far been small, seldom and often reliant on high frequency AC electronics. To overcome this limitation, in this work we consider a mechanical resonator suspended between two superconducting contacts to form a suspended Josephson junction in which the electronic normal- and super-currents can be coupled to mechanical motion via the Lorentz force due to an external magnetic field. We show both analytically and numerically that this electro-mechanical coupling produces unprecedented mechanically-induced hysteresis loops in the junction's DC I-V characteristic. Firstly, we unveil how this new hysteresis may be exploited to access a huge mechanically-induced Shapiro-like voltage plateau, extending over a current range comparable with the junction's critical current. We then investigate a sudden mechanically-induced retrapping that occurs at strong coupling. Our analytical treatment provides a clear explanation for the effects above and allows us to derive simple relationships between the features in the DC I-V characteristic and the resonance frequency and quality factor of the mechanical resonator. We stress that our setup requires only DC current bias and voltage measurements, allowing the activation and detection of high-frequency mechanical oscillations in state of the art devices and without the need of any AC equipment.