Low-temperature AFM with a microwave cavity optomechanical transducer

TL;DR

This paper introduces a low-temperature AFM technique utilizing a superconducting microwave resonant circuit integrated with a microcantilever, enhancing force sensitivity and approaching quantum-limited detection.

Contribution

The work presents a novel AFM force sensor based on cavity optomechanics with superconducting circuits, demonstrating improved sensitivity over traditional piezoelectric sensors at low temperatures.

Findings

The sensor operates near the thermal-noise limit.

Effective temperature of the cantilever eigenmode is determined.

AFM imaging achieved with surface-tracking feedback in multiple modes.

Abstract

We demonstrate AFM imaging with a microcantilever force transducer where an integrated superconducting microwave resonant circuit detects cantilever deflection using the principles of cavity optomechanics. We discuss the detector responsivity and added noise pointing to its crucial role in the context of force sensitivity. Through analysis of noise measurements we determine the effective temperature of the cantilever eigenmode and we determine the region of detector operation in which the sensor is thermal-noise limited. Our analysis shows that the force-sensor design is a significant improvement over piezoelectric force sensors commonly used in low-temperature AFM. We discuss the potential for further improvement of the sensor design to achieve optimal detection at the standard quantum limit. We demonstrate AFM operation with surface-tracking feedback in both amplitude-modulation and frequency-modulation modes.