Operating Nanobeams in a Quantum Fluid

TL;DR

This paper demonstrates the successful operation of nanobeams in superfluid helium, enabling sensitive detection of superfluid properties and paving the way for quantum mechanical studies at ultra-low temperatures.

Contribution

First successful measurement of NEMS resonators in superfluid helium, showing their potential for quantum fluid research and low-temperature quantum state exploration.

Findings

Nanobeams operate effectively in superfluid $^4$He.

Devices detect superfluid density and damping.

Potential to reach quantum ground state in superfluid $^3$He.

Abstract

Microelectromechanical (MEMS) and nanoelectromechanical systems (NEMS) are ideal candidates for exploring quantum fluids since they can be manufactured reproducibly, cover the frequency range from hundreds of kilohertz up to gigahertz and usually have very low power dissipation. Their small size offers the possibility of probing the superfluid on scales comparable to, and below, the coherence length. That said, there have been hitherto no successful measurements of NEMS resonators in the liquid phases of helium. Here we report the operation of doubly-clamped aluminum nanobeams in superfluid $^4$He at temperatures spanning the superfluid transition. The devices are shown to be very sensitive detectors of the superfluid density and the normal fluid damping. However, a further and very important outcome of this work is the knowledge that now we have demonstrated that these devices can be successfully operated in superfluid $^4$He, it is straightforward to apply them in superfluid $^3$He which can be routinely cooled to below 100\,$\mu$K. This brings us into the regime where nanomechanical devices operating at a few MHz frequencies may enter their mechanical quantum ground state.