Self-sustained oscillations of a torsional SQUID resonator induced by Lorentz-force back-action

• Published in: Nature communications 2013-04, Vol.4 (1), p.1803-1803, Article 1803
• Main Authors: Etaki, S., Konschelle, F., Blanter, Ya. M., Yamaguchi, H., van der Zant, H. S. J.
• Format: Article
• Language: English
• Subjects: 639/766/119; 639/925/927/359; Condensed Matter; Humanities and Social Sciences; Mesoscopic Systems and Quantum Hall Effect; multidisciplinary; Physics; Science; Science (multidisciplinary); Superconductivity
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms2827

For the study of nanomechanical resonators, ultra-sensitive measurement techniques are crucial. However, if the measurement sensitivity approaches quantum-mechanical limits, the back-action of the detector on the resonator cannot be neglected. If the back-action is strong enough, the corresponding instability can create self-sustained oscillators in the resonator. Here we demonstrate that a torsional mechanical resonator, which contains a direct current SQUID displacement detector, leads to this effect. We find that the Lorentz-force back-action can be so large that, in combination with complex nonlinear Josephson dynamics, it generates intrinsic self-sustained oscillations. The flux quantization limit of the maximum oscillation amplitude is exploited to calibrate the displacement resolution, which is shown to be below the standard quantum limit. The suspended torsional SQUID provides an interesting platform to study on-chip laser-like physics in an electromechanical system that can be controlled by both a flux and current bias. If the measurement sensitivity reaches the quantum limit during ultra-sensitive measurements, nanomechanical resonators interact with the detectors. Here the authors exploit this back-action to create and tune self-sustained electromechanical oscillations in a SQUID measurement system.