Sensitivity of the mixing current technique to detect nano-mechanical motion

TL;DR

This paper theoretically investigates the sensitivity limits of the mixing current technique used for detecting nano-mechanical motion, focusing on response function, noise, and tunneling effects to establish upper bounds.

Contribution

It provides a systematic analysis of factors affecting the sensitivity of the mixing current detection method for nano-mechanical oscillators, including noise and tunneling rate effects.

Findings

Sensitivity increases with response function enhancement.

Noise reduction improves detection limits.

Upper bounds on sensitivity are established based on tunneling rates.

Abstract

Detection of nano-mechanical displacement by transport techniques has reached high level of sensitivity and versatility. In order to detect the amplitude of oscillation of nano-mechanical oscillator a widely used technique consists to couple this motion capacitively to a single-electron transistor and to detect the high-frequency modulation of the current through the non-linear mixing with an electric signal at a slighltly detuned frequency. The method known as current-mixing technique is employed in particular for the detection of suspended carbon nanotubes. In this paper we study theoretically the limiting conditions on the sensitivity of this method. The sensitivity is increased by increasing the response function to the signal, but also by reducing the noise. For these reasons we study systematically the response function, the effect of current-and displacement-fluctuations, and finally the case where the tunnelling rate of the electrons are of the same order or larger of the resonating frequency. We find thus upper bounds to the sensitivity of the detection technique.