Abstract
Superfluids, such as superfluid and , exhibit a broad range of quantum phenomena and excitations which are unique to these systems. Nanoscale mechanical resonators are sensitive and versatile force detectors with the ability to operate over many orders of magnitude in damping. Using nanomechanical-doubly clamped beams of extremely high quality factors (), we probe superfluid from the superfluid transition temperature down to millikelvin temperatures at frequencies up to 11.6 MHz. Our studies show that nanobeam damping is dominated by hydrodynamic viscosity of the normal component of above 1 K. In the temperature range of 0.3–0.8 K, the ballistic quasiparticles (phonons and rotons) determine the beams' behavior. At lower temperatures, damping saturates and is determined either by magnetomotive losses or by acoustic emission into helium. It is remarkable that all these distinct regimes can be extracted with just a single device, despite damping changing over six orders of magnitude.
- Received 17 May 2019
- Revised 13 June 2019
DOI:https://doi.org/10.1103/PhysRevB.100.020506
©2019 American Physical Society
Physics Subject Headings (PhySH)
Synopsis
A New Tool for Sensing Phonons in Liquid Helium
Published 17 July 2019
Nanomechanical resonators probe helium-4 at record low temperatures in a proof-of-concept experiment demonstrating the potential to explore fundamental properties of quantum fluids.
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