Mechanical frequency control in inductively coupled electromechanical systems

TL;DR

This paper demonstrates how the resonance frequency of a nano-electromechanical system with a SQUID can be precisely controlled using magnetic flux and bias fields, with implications for tunable quantum devices.

Contribution

It introduces two novel methods for controlling mechanical resonance frequency in inductively coupled nano-electromechanical systems using magnetic flux and bias fields.

Findings

Resonance frequency can be tuned via bias magnetic flux.

Resonance frequency can be adjusted by in-plane magnetic field.

Residual shifts due to vortex flux pinning observed.

Abstract

Nano-electromechanical systems implement the opto-mechanical interaction combining electromagnetic circuits and mechanical elements. We investigate an inductively coupled nano-electromechanical system, where a superconducting quantum interference device (SQUID) realizes the coupling. We show that the resonance frequency of the mechanically compliant string embedded into the SQUID loop can be controlled in two different ways: (i) the bias magnetic flux applied perpendicular to the SQUID loop, (ii) the magnitude of the in-plane bias magnetic field contributing to the nano-electromechanical coupling. These findings are quantitatively explained by the inductive interaction contributing to the effective spring constant of the mechanical resonator. In addition, we observe a residual field dependent shift of the mechanical resonance frequency, which we attribute to the finite flux pinning of vortices trapped in the magnetic field biased nanostring.