Fully suspended nano-beams for quantum fluids

Abstract

Non-invasive probes are keystones of fundamental research. Their size, and maneuverability (in terms of e.g. speed, dissipated power) define their applicability range for a specific use. As such, solid state physics possesses e.g. Atomic Force Microscopy (AFM), Scanning Tunneling Microscopy (STM), or Scanning SQUID Microscopy. In comparison, quantum fluids (superfluid ${}^3$He, ${}^4$He) are still lacking probes able to sense them (in a fully controllable manner) down to their smallest relevant lengthscales, namely the coherence length ${\xi }_0$. In this work we report on the fabrication and cryogenic characterization of fully suspended (hanging over an open window, with no substrate underneath) Si${}_3$N${}_4$ nano-beams, of width down to 50 nm and quality factor up to $10^5$. As a benchmark experiment we used them to investigate the Knudsen boundary layer of a rarefied gas: ${}^4$He at very low pressures. The absence of the rarefaction effect due to the nearby chip surface discussed in Gazizulin et al. [1] is attested, while we report on the effect of the probe size itself.

References in corpus (5)

• Generalized Knudsen Number for Unsteady Fluid Flow
• Layering transitions in superfluid helium adsorbed on a carbon nanotube mechanical resonator
• Nanoscale Real-Time Detection of Quantum Vortices at Millikelvin Temperatures
• Visualizing Pure Quantum Turbulence in Superfluid ${}^3$He: Andreev Reflection and its Spectral Properties
• Surface-induced near-field scaling in the Knudsen layer of a rarefied gas

Cited by in corpus (1)

• Nano-beam clamping revisited