Driving nanomechanical resonators by phonon flux in superfluid \(\mathbf{^4He}\)

TL;DR

This paper demonstrates high-quality nanomechanical resonators operated in superfluid helium, using phonon flux to drive them, enabling new optomechanical experiments in quantum fluids at millikelvin temperatures.

Contribution

It introduces the first demonstration of driving nanomechanical resonators via phonon flux in superfluid helium, revealing new methods for quantum fluid optomechanics.

Findings

Resonators exhibit high quality factors in superfluid helium.

Phonon wind can effectively drive nanomechanical resonators.

Damping mechanisms mapped across temperature range.

Abstract

We report on nanomechanical resonators with very high-quality factors operated as mechanical probes in liquid helium \(^4\mathrm{He}\), with special attention to the superfluid regime down to millikelvin temperatures. Such resonators have been used to map out the full range of damping mechanisms in the liquid on the nanometer scale from \(10\,\mathrm{mK}\) up to \(\sim3\,\mathrm{K}\). The high sensitivity of these doubly-clamped beams to thermal excitations in the superfluid \(^4\mathrm{He}\) makes it possible to drive them using the momentum transfer from phonons generated by a nearby heater. This so-called "\textit{phonon wind}" is an inverse thermomechanical effect that until now has never been demonstrated, and provides the possibility to perform a new type of optomechanical experiments in quantum fluids.