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تسجيل مستخدم جديدDetecting the phonon wind in superfluid $mathrm{^4He}$ by a nanomechanical resonator
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Nanoscale mechanical resonators are widely utilized to provide high sensitivity force detectors. Here we demonstrate that such high quality factor resonators immersed in superfluid (^4mathrm{He}) can be excited by a modulated flux of phonons. A nanosized heater immersed in superfluid (^4mathrm{He}) acts as a source of ballistic phonons in the liquid -- phonon wind. When the modulation frequency of the phonon flux matches the resonance frequency of the mechanical resonator, the motion of the latter can be excited. This ballistic thermomechanical effect can potentially open up new types of experiments in quantum fluids.
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We report on nanomechanical resonators with very high-quality factors operated as mechanical probes in liquid helium (^4mathrm{He}), with special attention to the superfluid regime down to millikelvin temperatures. Such resonators have been used to m
ap 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 (^4mathrm{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.
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