Damping of a Micro-electromechanical Resonator in the Presence of Quantum Turbulence Generated by a Quartz Tuning Fork
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Damping of a Micro-electromechanical Resonator in the Presence of Quantum Turbulence Generated by a Quartz Tuning Fork C. S. Barquist1
· W. G. Jiang1 · K. Gunther1 · Y. Lee1 · H. B. Chan2
Received: 1 September 2019 / Accepted: 6 December 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract A micro-electromechanical resonator, consisting of a 125 × 125 µm2 center plate suspended 2 µm above a substrate, was immersed in 4 He along with a quartz tuning fork. The tuning fork was placed 5 mm above the resonator and was used to generate turbulence. The damping of the resonator was investigated in the presence of turbulence generated by the tuning fork. We observe a velocity, vc 5 mm s−1 , above which the damping on the resonator is drastically reduced for all tuning fork velocities studied. We attribute this change in damping to the shedding and capture of vortices. Keywords Quantum turbulence · Mechanical resonator · He II · Vortex · Critical velocity
1 Introduction Turbulence, or more generally chaos in dynamical systems, is becoming an ever more important and interesting area of research as we seek to understand the structure of systems with a large number of interacting parts. In the low-temperature limit, where the normal fluid can be considered absent, superfluid turbulence offers a unique simplification over classical turbulence: All of the vorticity arises from identical quantized vortices, which have circulation κ = h/m, where h is Plank’s constant and
This work is supported by the National Science Foundation through DMR-1708818.
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C. S. Barquist [email protected] Y. Lee [email protected]
1
Department of Physics, University of Florida, Gainesville, FL 32611, USA
2
Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong
123
Journal of Low Temperature Physics
m is the mass of the boson responsible for the superfluidity. For superfluid 4 He, κ = 9.97 × 10−8 m2 s−1 . In the past several decades, a significant amount of work has been done to understand the nature of superfluid turbulence [1–3]. In the low-temperature limit, resonating structures have proven useful for generating turbulence and for studying the transition from laminar to turbulent flow. For this task, a plethora of different resonators has been used, including tuning forks [4,5], vibrating wires [6,7], microspheres [8], oscillating grids [9,10], and now micro- and nano-electromechanical (MEMS and NEMS) oscillators [11–13]. In superfluid 3 He-B, vibrating wires have been shown to be a detector of the local vortex line density [14–18]. This is because in 3 He-B the thermal quasiparticles, responsible for damping the wire, are efficiently Andreev-reflected by vortices around the device, resulting in a measurable decrease in the resonance linewidth. Unfortunately, no such mechanism exists in 4 He, and resonating structures are mostly unable to continuously detect turbulence generated by secondary structures [19] (e.g., a separate tuning fork). The Osaka City gr
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