Showing papers by "Yu. A. Pashkin published in 2020"
TL;DR: In this article, a nanoscale resonant beam is used to trap a single vortex along the length of a nanobeam and observe the transitions as a vortex is either trapped or released, which is observed through the shift in the resonant frequency of the beam.
Abstract: Since we still lack a theory of classical turbulence, attention has focused on the conceptually simpler turbulence in quantum fluids. Can such systems of identical singly-quantized vortices provide a physically accessible "toy model" of the classical counterpart? That said, we have hitherto lacked detectors capable of the real-time, non-invasive probing of the wide range of length scales involved in quantum turbulence. However, we demonstrate here the real-time detection of quantum vortices by a nanoscale resonant beam in superfluid $^4$He at 10 mK. The basic idea is that we can trap a single vortex along the length of a nanobeam and observe the transitions as a vortex is either trapped or released, which we observe through the shift in the resonant frequency of the beam. With a tuning fork source, we can control the ambient vorticity density and follow its influence on the vortex capture and release rates. But, most important, we show that these devices are capable of probing turbulence on the micron scale.
10 citations
TL;DR: In this article, a nanosized heater immersed in superfluid He-4 acts as a source of ballistic phonons in the liquid "phonon wind", when the modulation frequency of phonon flux matches the resonance frequency of the mechanical resonator, the motion of the latter can be excited.
Abstract: Nanoscale mechanical resonators are widely utilized to provide high sensitivity force detectors. Here we demonstrate that such high-quality-factor resonators immersed in superfluid He-4 can be excited by a modulated flux of phonons. A nanosized heater immersed in superfluid He-4 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.
10 citations
TL;DR: In this article, a quantum dot thermometer is calibrated using radio-frequency reflectometry and calibrated by fitting a physical model to the phase of the reflected radiofrequency signal taken at temperatures across a small range.
Abstract: A cryogenic quantum dot thermometer is calibrated and operated using only a single non-galvanic gate connection. The thermometer is probed with radio-frequency reflectometry and calibrated by fitting a physical model to the phase of the reflected radio-frequency signal taken at temperatures across a small range. Thermometry of the source and drain reservoirs of the dot is then performed by fitting the calibrated physical model to new phase data. The thermometer can operate at the transition between thermally broadened and lifetime broadened regimes, and outside the temperatures used in calibration. Electron thermometry was performed at temperatures between $3.0\,\mathrm{K}$ and $1.0\,\mathrm{K}$, in both a $1\,\mathrm{K}$ cryostat and a dilution refrigerator. The experimental setup allows fast electron temperature readout with a sensitivity of $4.0\pm0.3 \, \mathrm{mK}/\sqrt{\mathrm{Hz}}$, at Kelvin temperatures. The non-galvanic calibration process gives a readout of physical parameters, such as the quantum dot lever arm. The demodulator used for reflectometry readout is readily available and very affordable.
5 citations