Journal of Low Temperature Physics最新文献

Any experiment aiming to measure rare events, like Coherent Elastic neutrino-Nucleus Scattering (CE(upnu)NS) or hypothetical Dark Matter scattering, via nuclear recoils in cryogenic detectors relies crucially on a precise detector calibration at sub-keV energies. The Crab collaboration developed a new calibration technique based on the capture of thermal neutrons inside the target crystal. Together with the Nucleus experiment, first measurements with a moderated (^{252})Cf neutron source and a cryogenic ({{textrm{CaWO}}_4}) detector were taken. We observed for the first time the 112eV peak caused by the (^{182})W(n, ({upgamma }))(^{183})W capture reaction and subsequent nuclear recoils. Currently, Crab is preparing a precision measurement campaign based on a monochromatic flux of thermal neutrons from the 250-kW Triga-mark II nuclear reactor at TU Wien. In this contribution, we introduce the Crab technique, present the first measurement of the 112eV peak, report the preparations for the precision measurement campaign, and give an outlook on the impact on the field of cryogenic detectors.

This paper presents a comparative study of various light detectors (LDs) developed for different phases of the AMoRE neutrinoless double beta decay experiment. We analyze the performance of these detectors in terms of characteristics such as time response, light collection, and energy resolution. Our primary focus is on evaluating the performance of the AMoRE-II light detector, which is integral to the forthcoming AMoRE-II experiment. It is found that AMoRE-II type LDs outperform other previous light detector types. The best-performing LD exhibits FWHM energy resolution of 99, 198, 198, and 481 eV for baseline and ⁵⁵Fe X-ray energies of 5.9, 6.5, and 17.5 keV molybdenum X-ray, respectively. We adopted a convolution method to estimate the energy of the scintillation signals from 2.615 MeV gamma rays fully absorbed in a lithium molybdate crystal. The measured energy of scintillation light with AMoRE-II type LDs falls in the range of 2.1–2.5 keV, which corresponds to 0.80–0.96 keV/MeV. This measured energy is approximately 14–39(%) higher than that measured with previous LD types for the experiments.

In a Josephson junction, the supercurrent is determined by both the discrete sub-gap part of the spectrum due to Andreev bound states and the continuous part of the spectrum from energy states outside the superconducting gap. We consider the cohesive force exerted on a junction, which is thermodynamically conjugated to the superflow, and comment on its connection to the Casimir effect in quantum electrodynamics. In contrast to the supercurrent, it is shown that in ballistic short junctions, the force is predominantly contributed by the continuum. Its magnitude is universally defined by the energy gap and coherence length of the superconductor per spin-dependent transverse mode. This force scales non-analytically with the junction length and is periodic with the superconducting phase. For long ballistic junctions, the force results from the interplay of oscillatory contributions originating from both bound states and the continuum. The resulting asymptotic limit for the force is established, including the correction terms. Thermal and impurity effects on the force are briefly discussed.

The infinite time-evolving block decimation (iTEBD) algorithm provides an efficient way to search for the ground state of a one-dimensional lattice system with translational invariance at the thermodynamic limit, especially for systems with limited entanglement. However, for systems with large on-site physical degrees of freedom, especially for the antiferromagnetic Heisenberg (AFH) chain with SU(N) symmetries, the decompositions in the iTEBD calculation become extremely heavy, even for a small virtual bond dimension. In this work, we consider a revised low-rank approximation by Monte Carlo sampling in the decomposition process. Our results show that compared to the original iTEBD algorithm, the proposed algorithm achieves faster convergence with comparable accuracy. Based on this algorithm, we calculate the ground state energy of the SU(3) AFH model with representation (varvec{10}) and find evidence that the ground state belongs to a trivial symmetry-protected topological phase.

In this work, the patterns of changes in concentration, density of thermodynamic states, thermodynamic potential, entropy and heat capacity of electron gas under the influence of hydrostatic pressure and temperature were studied in nanowires in the form of a rectangular potential well, obtained on the basis of semiconductors with narrow bandgaps. The patterns of changes in the effective mass, nonparabolicity coefficient and energy levels of electron gas in nanowires under the influence of temperature and hydrostatic pressure are determined. An increase in the steepness and a narrowing between turns of oscillation were determined on the graph of the dependence of the chemical potential on thermodynamic quantities in semiconductor nanowires with increasing hydrostatic pressure. The decrease in the steepness and the expansion between oscillation cycles on the graph of the dependence of the chemical potential on the thermodynamic properties of the semiconductor nanowires with increasing temperature were determined. The disappearance of oscillations at high temperatures and the observation of oscillations at low temperatures are shown on the graph of the dependence of thermodynamic values on the chemical potential. The dependence of the concentration, density of thermodynamic states, thermodynamic potential, entropy and heat capacity of the electron gas in InAs nanowires, on the chemical potential and the energy level (mu <E_{left( N,Lright) }), (mu =E_{left( N,Lright) }) and (mu >E_{left( N,Lright) }) on the hydrostatic pressure and temperature are consistent.

Since the 1940 s, intensive studies of (^3)He viscosity have demonstrated the ultra-low-temperature behavior (T^{-2}) predicted by Landau’s Fermi liquid(FL) theory. Unexpectedly, it turns out that within one order of magnitude in temperature up to (^3)He evaporation, the experimental data obey a mysterious power law (T^{-1/3}) out of any theoretical ground. Based on conventional Fermi gas approach we consider a small but important fraction of fermions located in the thermal vicinity of the Fermi energy and, then directly find the fermion-fermion mean free path. Subsequent calculation of viscosity reveals a puzzling dependence of the negative one-third on temperature. We compare our results with longstanding experimental findings. For two-dimensional electron gas an negative one-half law on temperature is predicted.

The gas-gap heat switch, with its stability and reliability, high switching ratio, and a design that is simple, flexible, and easily scalable, has become the preferred option for efficient pre-cooling in various low-temperature devices such as dilution refrigerators. We have successfully developed a differential thermal expansion type of gas-gap heat switch. This paper details its basic principles, fabrication process, performance testing, and preliminary application in dilution refrigerator system. The typical thermal conductivity of the gas-gap heat switch in the temperature range of 4–30 K has been experimentally measured in both ON and OFF states, and the results are generally consistent with the calculated data. Tests in a dilution refrigerator with a cooling power of approximately 400 μW at 100 mK showed that the developed gas-gap heat switch assembly could perform its functions of thermal connection and disconnection properly and reduce the temperature of the still cold plate to about 7 K within roughly 24 h, significantly improving the original cooling time. Additionally, its heat leakage in the millikelvin temperature range does not affect the attainment of temperatures around 10 mK. Finally, combining the calculated results, we quantitatively analyzed the impact and feasible solutions for the performance improvement of this type of gas-gap heat switch. The research work presented in this paper is of reference value for efficient pre-cooling in dilution refrigerators and other low-temperature equipment.

The AMoRE collaboration conducts experiments to search for the neutrinoless double beta decay of (^{100})Mo using massive (hbox {Li}_{2}hbox {MoO}_{4}) (LMO) crystals in a cryogenic calorimetric detection with metallic magnetic calorimeters (MMCs). The detector module incorporates a light detector with Si or Ge wafers, enabling the simultaneous detection of scintillation light. The forthcoming phase (AMoRE-II) of the experiment will include 6 cm (diameter) (times) 6 cm (height) LMO cylindrical crystals, and this has been chosen to reduce the number of crystals and sensors. Additionally, these crystals will have diffusive surfaces rather than polished ones, which helps to reduce the crystal preparation time. The phonon signal of crystals with diffusive surfaces is slower than that of polished crystals. However, due to the mitigated position dependence, diffusive crystals exhibit better discrimination between (alpha) and (beta)/(gamma) signals by pulse shape analysis. We also found that muon events show two bands in the rise time of the large LMO crystal with polished surface, indicating the muon passage at the edge of the crystal, and the band structure is significantly mitigated in the crystals with the diffusive surfaces. To study the position dependence in the crystal absorber further, we irradiated some R&D detectors with localized (alpha) sources. This paper discusses the particle identification and position dependence of (gamma), (alpha), and muon events for the large AMoRE-II type detectors based on the pulse shape analysis.

If we confine superfluid helium in two bulk chambers, named A and B, connected by a tube, it is known that heat injected into chamber A will force the normal-fluid component to flow from chamber A to B and the superfluid component to flow in the opposite direction. We also know that quantum turbulence can be generated by this thermal counterflow when it exceeds critical values. We measured the vortex line density by the second sound attenuation in chambers A and B. The results showed that the heater power required for the turbulence transition was lower in chamber B than in chamber A, even though the superfluid was flowing toward chamber A. This asymmetry suggests that the mechanisms for generating turbulence in each chamber are different. In chamber A, the quantum turbulence was generated by the thermal counterflow converging toward the tube near the inlet of the tube. In chamber B, in contrast, it was generated while simultaneously being transported by the counterflow jet flowing out of the tube.

We consider Bose–Einstein condensates with helicoidal spin-orbit coupling and study spin-mixing properties of a pseudo-spin 1/2 system through fixed point analysis. At the equilibrium condition, strength of the helicoidal gauge potential plays a significant role to create initial spin imbalance in the two-level system. The spin flipping between the two states occurs with time in the non-equilibrium condition. We see that the changes of spin imbalance with time between the two states execute periodic or quasi-periodic patterns. Amplitude and frequency of the oscillation dynamics depend sensitively on the helicoidal spin-orbit coupling and atomic interaction. We show that spin-mixing dynamics lead to various types of phase-space trajectories with the change of initial spin imbalance and helicoidal gauge potential.