Journal of Low Temperature Physics最新文献

This work experimentally explores the induction of resistive transitions in a metal through the magnetic proximity effect, focusing specifically on the transitions in the electrical resistance of copper induced by the magnetic transitions of copper oxychloride. The findings unveiled a sharp drop in the electrical resistance of the conductive channel within the metallized regime, precisely coinciding with the magnetic transitions of copper oxychloride. The study’s findings align with prior research on spin resistivity in frustrated antiferromagnet, and this phenomenon can be attributed to the induction of triplet states within the metallic layer via the magnetic proximity effect. These insights hold the potential to unlock new avenues for the investigation of spintronic devices and magnetic interface phenomena.

Liquid helium has important applications in infrared wavelength detection, superconducting quantum interference, and so on. Regenerative refrigerators are generally applied for small-scale applications. However, the liquefaction efficiency of helium is not high. The main reason is the contradiction between the large sensible heat load and the limited refrigeration efficiency at 4.2 K. A novel method of temperature-distributed regenerative refrigeration, which generates the refrigeration power over a wide temperature range based on real gas effects, is theoretically studied using the ³He working fluid for the first time. The liquefaction rate and efficiency of helium is improved because of a smaller entropy generation with this temperature-distributed method. The temperature-distributed refrigeration power of the ³He working fluid is larger than that of ⁴He when the absolute pressure is smaller, because the critical pressure of ³He is lower; while such a refrigeration power of ³He distributes at a lower temperature range that of ⁴He at the same reduced pressure because the critical temperature of ³He is lower. The liquefaction rate reaches 50.5 L/d when the cold-end refrigeration power is 1.5 W. This rate is 2–3 times that of liquefying with only the cold end with ⁴He or ³He. Furthermore, the liquefaction efficiency (FOM) increases with the rise in pressure. The theoretical FOM is 47.7% at a reduced pressure of 61.7 (14.1 MPa), which is a 7% improvement over the case with ⁴He (44.7%). These results demonstrate advantages of using the temperature-distributed method with ³He, thus opening up a new avenue for further researches in helium liquefaction systems.

(alpha)-W thin films are widely used in superconducting transition edge sensors due to their extremely low transition temperature and weak electron–phonon coupling. However, the influence of annealing and substrate temperatures on thin film performance has not been fully understood, nor has the relationship between microstructure and thin film performance. In this study, we investigate the changes in grain size, resistivity, film stress, and transition temperature of the film by varying the annealing and substrate temperatures. Microstructure showed that annealing contributed to grain growth. With the increase in annealing temperature, the resistivity of the film decreased and the compressive stress was relieved. The minimum transition temperature reached 28.7 mK at an annealing temperature of (470 ^{circ })C. In addition, the GIXRD results showed that the preferred orientation of the films changed from (110) to (211) with the increase in the substrate temperature. (100 ^{circ }hbox {C}-230 ^{circ })C favorite to reduce film resistivity and transition temperature, and to relieve film compressive stress.

We synthesized an Ag:Er alloy having paramagnetic properties to be used as a temperature sensor in metallic magnetic calorimeters. The Ag:Er master alloy and a 2-inch target for film deposition were, respectively, manufactured using vacuum arc melting and RF heating under process conditions designed to minimize impurity contamination. Calculations and measurements of magnetization versus magnetic field were employed to check for magnetic impurities in the host material, Ag, and to estimate the Er concentration in the Ag:Er alloy at each step of the synthesis. The temperature-dependent magnetization of deposited thin films from the synthesized Ag:Er with (^{168})Er isotope was measured in the mK range, demonstrating their suitability as temperature sensors for low-temperature detectors such as metallic magnetic calorimeters.

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.

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.

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.