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Journal of Low Temperature Physics
Journal Prestige (SJR): 0.471  Citation Impact (citeScore): 1 Number of Followers: 9  Hybrid journal (It can contain Open Access articles)ISSN (Print) 1573-7357 - ISSN (Online) 0022-2291 Published by Springer-Verlag  [2467 journals]
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- Simulation and Measurement of Out-of-Band Resonances for the FDM Readout
of a TES Bolometer-
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Abstract: Abstract With applications in cosmology, infrared astronomy and CMB survey, frequency-division multiplexing (FDM) proved to be a viable readout for transition-edge sensors (TESs). We investigate the occurrence of out-of-band resonances (OBR) which could constrain the bandwidth of the FDM readout of TES bolometers. The study includes SPICE modeling of the entire setup including the cryogenic harness, LC filters, Superconducting Quantum Interference Device (SQUID) and room-temperature amplifier. Simulation results show that the long harness (for flight model) could cause multiple reflections that generate repetitive spikes in the spectrum. Peaks of the OBR are mainly due to the parasitic capacitances at the input of SQUID. Implementing a low-pass RC circuit (snubber) at the input of the SQUID dampened the OBR. As a result, the first peak only appears around 20 MHz which is a safe margin for the 1 MHz \(-\) 3.8 MHz FDM in use in the prototype readout. Using a spectrum analyzer and broadband LNAs, we also measured the OBR for the prototype FDM readout in the laboratory up to 500 MHz. The measurement was conducted at temperatures of 50 mK and 4 K and for various biasing of the DC SQUID. It turns out that OBRs are more intense at 50 mK and are caused by the harness impedance mismatch rather than the SQUID. Simulation codes and supporting materials are available at https://github.com/githubamin/LT-Spice-Simulation-of-FDM-readout.
PubDate: 2023-03-17
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- Thermal Functions of Diatomic Molecules Using Hulthén Plus Screened
Kratzer Potential-
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Abstract: Abstract In the present paper, we have studied analytically the thermodynamic properties of diatomic molecules like LiH, HCl and H2 and compared calculated properties with experimental data. In this regard, we have solved the Schrödinger equation with Hulthén plus screened Kratzer potential using the Nikiforov–Uvarov method and obtained energy eigenvalues. According to calculated the energy eigenvalues, we have deduced the partition function and thermodynamic properties of the molecules by applying the Poisson summation formalism. Our results show that the specific heat at constant pressure, Gibbs free energy and enthalpy are in good agreement with experimental data The average deviation of the specific heat at constant pressure, Gibbs free energy and enthalpy is \(1.62 \%\) , \(3.57\%\) and \(4.21\%\) , respectively. It is obvious from the data that the potential model predicts well the thermodynamic properties of diatomic molecules.
PubDate: 2023-03-17
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- Impact of Impurity on the Mean Energy, Heat Capacity, Free Energy, Entropy
and Magnetocaloric Effect of Ga1-χAlχAs Quantum Wire-
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Abstract: Abstract In this work, the thermodynamic properties of a Ga1-χAlχAs quantum wire under a parabolic confinement potential, influence of Rashba SOI and presence of Al impurity are studied. External electric and magnetic fields have also been considered. We first formulate the Hamiltonian of the system and then find the eigenenergies, which are used to calculate the partition function. The partition function is the basis of formulating the thermodynamic properties under consideration, viz. mean energy, heat capacity, free energy, entropy and magnetocaloric effect, which are plotted against temperature and impurity. The results show that the mean energy rises with temperature, a peak structure is observed in the heat capacity and the magnetocaloric effect, the free energy steadily decreases with temperature, and the entropy first increases, and then converges to a constant value. The mean energy, heat capacity and free energy increase with impurity, whereas the magnetocaloric effect decreases. The behaviour of all the properties with respect to impurity reverses when the value of impurity becomes greater than ~ 0.6.
PubDate: 2023-03-17
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- Sixty Years of Quantized Circulation
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Abstract: Abstract Vinen’s vibrating wire experiment detected quantized vortices in superfluid \({}^4\) He, with the anticipated circulation quantum h/m. In addition to this main result, Vinen used his data to propose other properties and behaviors of vortices, which are revisited here. Subsequent work confirmed that non-quantized values occur when vortices cover only part of the wire’s length and that the size of the covered section can change easily. Any motion of the detached portion of the vortex induces changes in the circulation around the wire, which provides a means of tracking the free vortex. Particularly distinctive signatures correspond to a circular motion of the vortex through the cell and to Kelvin waves along the free vortex. Another issue, the lack of stability of multi-quantum states, can also be explained through simple arguments, in which the possibility of a partially detached vortex again plays a key role. Vibrating wire measurements descended from Vinen’s continue to probe superfluid flows.
PubDate: 2023-03-16
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- Polarized Bolometer, a New Tool Essential to Neutrino Physics'
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Abstract: Abstract A polarized bolometer may become an essential tool to study the scattering of neutrinos because these particles are intrinsically polarized in their direction of propagation. Polarized solid targets were widely used in nuclear and high-energy physics during the sixties. Later on, many studies were conducted with gases (Xe139 and He3) for NMR medical purposes. In their paper, Tarso Franarin and Malcolm Fairbairn (Phys. Rev D 94: 053004) show that a polarized target, in fact gaseous He3, can change the interaction strength between the neutrino and the target, in the best case to suppress it leaving the possibility to search for dark matter, even with the floor of solar neutrinos. We take advantage of the polarization to modify the interaction, changing the part coming from the axial interaction. In this paper, we recall an old but well-known procedure to polarize nuclei embedded in a dielectric solid and indicate interesting paths for different nuclei which appear as promising targets for neutrino scattering and therefore for neutrino physics.
PubDate: 2023-03-09
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- Studies on Quantum Turbulence with Vinen
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Abstract: Abstract In my research career in the field of quantum turbulence, I have been encouraged by Vinen. In this article, I review my works motivated by him and my joint collaborations with him. Vinen encouraged me in studies on quantum turbulence at zero temperature, Kolmogorov spectrum of a vortex tangle without mutual friction, and fully coupled dynamics of quantized vortices and normal fluid. Joint works include studies on diffusion of a vortex tangle, Kelvin wave cascade, quantum turbulence created by an oscillating object, and coupled dynamics of tracer particles and quantized vortices.
PubDate: 2023-03-09
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- Performance of Two-phase Closed Loop Thermosyphon in Cooling Down of
Compact Superconducting Magnet-
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Abstract: Abstract An experiment to investigate the two-phase closed loop thermosyphon (TPCLT) to cooling the compact superconducting magnet has been performed. This study is motivated mainly by our development of cryogenic cooling for a superconducting cyclotron magnet system. In the two-phase closed loop thermosyphon system, the cooling of the cold mass (27 kg copper block) from room temperature to 4 K is achieved in three stages by refilling subsequently the loop with Nitrogen (80 K), Neon (30 K) and Helium (4 K) based on the different boiling point of each of the gases. The cooldown process and efficiency were analyzed and compared with directly conductor cooling method. The results show that the TPCLT cooling method can reduce the liquid helium and shorten the cooling time, so it has a potential to achieve lower energy consumption and higher efficiency for cooling compact a superconducting magnet (the weight large than 100 kg) in practical applications.
PubDate: 2023-03-09
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- Thermodynamic Properties and Persistent Currents of Harmonic Oscillator
Under AB-Flux Field in a Point-Like Defect with Inverse Square Potential-
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Abstract: Abstract In this analysis, we study the eigenvalue solution of the non-relativistic particles confined by the Aharonov-Bohm (AB) flux field in the presence of potential the superposition of a harmonic oscillator plus inverse square potential with constant term in the background of a point-like global monopole. Afterwards, we study the thermodynamic properties of the quantum system at finite temperatures \(T\ne 0\) and calculate the vibrational free energy, mean energy, specific heat capacity, and the entropy by using the partition function \(Z(\beta )\) . These quantities are then analyzed and show the influences of the topological defect with flux field and potential. We also see that the energy eigenvalue depends on the geometric quantum phase, and thus an electromagnetic analogue of the Aharonov-Bohm effect is observed. This dependence of the eigenvalue gives rise to a persistent current and we analyze the effects of the topological defect with potential on it.
PubDate: 2023-03-09
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- Fully Suspended Nano-beams for Quantum Fluids
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Abstract: Abstract Non-invasive probes are keystones of fundamental research. Their size and maneuverability (in terms of, for example, 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 characterisation of fully suspended (hanging over an open window, with no substrate underneath) \({\text {Si}}_{3} {\text {N}}_{4}\) 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. (Phys Rev Lett 120:036802, 2018. https://doi.org/10.1103/PhysRevLett.120.036802) is attested, while we report on the effect of the probe size itself.
PubDate: 2023-03-01
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- High Quality Quasinormal Modes of Phononic Crystals for Quantum
Acoustodynamics-
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Abstract: Abstract Phononic crystals are a promising platform for the study of quantum acoustodynamics. In a recent experiment, the interaction of a superconducting quantum bit with modes of a phononic crystal has been demonstrated. The field of these modes is localized in a compact area, providing high values of the coupling constant with the qubit. However, the Q-factor of phononic crystal modes is strongly limited ( \(\sim\) 1050) due to a phonon emission from the crystal ends. For further use of phononic crystals in research in the field of quantum acoustodynamics, it is desirable to overcome this limitation in the quality factor. In this work, we have proposed a structure consisting of a phononic crystal placed between the Bragg mirrors. Our simulations predict that the Q-factor in such a structure can reach ( \(\sim\) 100000). We demonstrate experimental results in which this structure has a Q-factor ( \(\sim\) 60,000), which is 60 times higher than that of an acoustic crystal of the same size.
PubDate: 2023-03-01
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- Vortex Shedding from a Microsphere Oscillating in Superfluid $$^4$$ He at
mK Temperatures and from a Laser Beam Moving in a Bose–Einstein
Condensate-
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Abstract: Abstract Turbulent drag of an oscillating microsphere that is levitating in superfluid \(^4\) He at mK temperatures, is unstable slightly above a critical velocity amplitude \(v_c\) . The lifetime \(\tau\) of the turbulent state is determined by the number n of vortices shed per half-period. It is found that this number is identical to the superfluid Reynolds number. The possibility of moving a levitating sphere through superfluid \(^3\) He at microkelvin temperatures is considered. A laser beam moving through a Bose–Einstein condensate (BEC) (as observed by other authors) also produces vortices in the BEC. In particular, in either case, a linear dependence of the shedding frequency \(f_v\) on \(\Delta v = v - v_c\) is observed, where v is the velocity amplitude of the sphere or the constant velocity of the laser beam above \(v_c\) for the onset of turbulent flow: \(f_v = a \,\Delta v\) , where the coefficient a is proportional to the oscillation frequency \(\omega\) above some characteristic frequency \(\omega _k\) and assumes a finite value for steady motion \(\omega \rightarrow 0\) . A relation between the superfluid Reynolds number and the superfluid Strouhal number is presented that is different from classical turbulence.
PubDate: 2023-03-01
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- Microwave Optomechanically Induced Transparency and Absorption Between 250
and 450 mK-
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Abstract: Abstract High-quality microwave amplifiers and notch-filters can be made from microwave optomechanical systems in which a mechanical resonator is coupled to a microwave cavity by radiation pressure. These amplifiers and filters rely on optomechanically induced transparency (OMIT) and absorption (OMIA), respectively. Such devices can amplify microwave signals with large, controllable gain, high dynamic range and very low noise. Furthermore, extremely narrowband filters can be constructed with this technique. We briefly review previous measurements of microwave OMIT and OMIA before reporting our own measurements of these phenomena, which cover a larger parameter space than has been explored in previous works. In particular, we vary probe frequency, pump frequency, pumping scheme (red or blue), probe power, pump power and temperature. We find excellent agreement between our measurements and the predictions of input/output theory, thereby guiding further development of microwave devices based on nanomechanics.
PubDate: 2023-03-01
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- IR Spectrometric Studies of CCL4 and Ar Gas Mixtures
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Abstract: Abstract IR spectrometric studies were performed to examine the cryo-deposition processes and properties of thin cryo-vacuum condensate films containing a mixture of carbon tetrachloride and argon, which were obtained by physical cryo-vacuum deposition at various concentrations. The measurements were carried out in a temperature range of 11–100 K, and the pressure of the gas phase was 10–8 Torr-10–4 Torr. The film thickness in all experiments performed was d = 2 μm. The vibrational spectra of CCl4 in an argon matrix were measured in a frequency range of 400–4200 cm−1 at mixture concentrations (CCl4 + Ar) of 10–90%, 5–95%, and 1–99% and after the argon matrix underwent sublimation. Thermal desorption curves for the yield of the matrix gas (Ar) were obtained in the temperature range of 40–90 K for the (CCl4 and Ar) system. It was found that the CCl4 molecules in the Ar matrix substance underwent cryocapture. The results obtained suggest that carbon tetrachloride can be used as a matrix in low-temperature studies on self-organization processes in thin films.
PubDate: 2023-02-27
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- Mechanical Resonators at Low Temperatures
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PubDate: 2023-02-24
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- Impacts of Cavitation on Flow Field Distributions and Pump Stability in
Cryogenic Pumps-
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Abstract: Abstract This study aims to investigate the impact of cavitation states on the stability of cryogenic pumps. Steady and unsteady simulations of the internal flow were conducted based on an SST k–ω turbulence model and a modified Zwart cavitation model considering thermodynamic effects. The modified cavitation model was verified using the hydrofoil model and compared with the Hord test results. The results indicate that the variation in pressure at the pump inlet has a significant influence on the cavitation in the pump. The cavitation states and fluid flow directions vary across the different spans in the impeller channel. The smaller the distance from the front cover of the impeller, the more severe is the cavitation, in addition to the appearance of a vortex. The influence of the formation of a longitudinal vortex at the impeller outlet on the pressure fluctuation in the cavitation state was revealed. The rotation of the impeller has negligible influence on the pressure load distribution at the blade inlet. However, it has a higher influence on that of the second half of the blade, particularly when the blade passes through the volute tongue. Cavitation can exacerbate the instability of pump operation. The research results are significant for accurately predicting cavitation performance and improving the anti-cavitation capability of cryogenic pumps.
PubDate: 2023-02-13
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- Vinen’s Energy Barrier
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Abstract: Abstract In 1963, the late W. F. (“Joe”) Vinen concluded, partly on intuitive grounds, that the ab initio creation of a quantized vortex line in superfluid \(^4\) He is impeded by an energy barrier. We place this prescient insight into context and review subsequent theoretical and experimental research that calculated the height of the barrier and validated the result through measurements on negative ions moving through superfluid \(^4\) He above the Landau critical velocity. We discuss the implications of these results for other superfluids, including laser-cooled dilute atomic gases, and for the subsequent development of superfluid hydrodynamics.
PubDate: 2023-02-13
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- Superfluid Drain Vortex
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Abstract: Abstract Drain vortices are among the most common vortices observed in everyday life, yet their physics is complex due to the competition of vorticity’s transport and diffusion, and the presence of viscous layers and a free surface. Recently, it has become possible to study experimentally drain vortices in liquid helium II, a quantum fluid whose physics is characterised by the absence of viscosity and the quantisation of the circulation in the superfluid component. Using the Gross–Pitaevskii equation, we make a simple model of the problem which captures the essential physics ingredients, showing that the drain vortex of a pure superfluid consists of a bundle of vortex lines which, in the presence of a radial drain, twist, thus strengthening the axial flow into the drain.
PubDate: 2023-02-07
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- Electron Propagation in Molybdenum Disulfide Quantum Dot in the Presence
of Magnetic Flux-
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Abstract: Abstract We investigate the Dirac electron scattering phenomenon in a molybdenum disulfide monolayer \(\mathrm {MoS}_2\) quantum dot that has been submitted to a magnetic flux \(\phi\) . Using the Dirac equation, we analytically determine the expressions for the eigenstates, the scattering efficiency, the scattering coefficients and the radial component of the reflected current. We identify different scattering regimes as a function of the physical parameters such as the incident electronic energy E, potential barrier V, radius R of the quantum dot, and magnetic flux \(\phi\) . We show that when the energy of the incident electron is low, scattering resonances appear and that the scattered current has different preferred scattering directions.
PubDate: 2023-02-04
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- Progress on Levitating a Sphere in Cryogenic Fluids
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Abstract: Abstract We present the working prototype of a levitation system designed for investigation of flows in cryogenic helium fluids. The current device allows the levitation of a superconducting sphere and has several provisions made for allowing precise control over its motion. We report on progress in the detection and control systems of the prototype and demonstrate how uniform circular motion can be implemented.
PubDate: 2023-02-04
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- Magnetic Cooling and Vibration Isolation of a Sub-kHz Mechanical Resonator
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Abstract: Abstract We report recent progress toward the realization of a sub-mK, low-vibration environment at the bottom stage of a dry dilution refrigerator for use in mechanical tests of quantum mechanics. Using adiabatic nuclear demagnetization, we have cooled a silicon cantilever force sensor to \(T\approx 1\) mK. The temperature of the tip holder of the cantilever chip was determined via a primary magnetic flux noise thermometer. The quality factor of the cantilever continues to increase with decreasing temperature, reaching \(Q\approx 4\cdot 10^4\) at 2 mK. To demonstrate that the vibration isolation is not compromised, we report the detection of the thermal motion of the cantilever down to \(T \approx 20\) mK, only limited by the coupling to the SQUID readout circuit. We discuss feasible improvements that will allow us to probe unexplored regions of the parameter space of continuous spontaneous localization models.
PubDate: 2023-02-04
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