Journal of Low Temperature Physics最新文献

Percent-level calibration of cryogenic macro-calorimeters with energy thresholds below 100 eV is crucial for light Dark Matter (DM) searches and reactor neutrino studies based on coherent elastic neutrino-nucleus scattering (CEvNS). This paper presents a novel calibration source based on X-ray fluorescence (XRF) of light elements. It uses a (^{55})Fe source to irradiate a two-staged target arrangement, emitting characteristic emission lines from 677 eV to 6.5 keV. We demonstrate the potential of this new XRF source to calibrate a 0.75 g CaWO(_4) crystal of the NUCLEUS and CRAB experiments. Additionally, we introduce CryoLab, an advanced analysis tool for cryogenic detector data, featuring robust methods for data processing, calibration, and high-level analysis, implemented in MATLAB and HDF5. We also present a phenomenological model for energy resolution, which incorporates statistical contributions, systematic effects, and baseline noise, enabling a novel approach to evaluating athermal phonon collection efficiency in macro-calorimeters based on transition edge sensors (TES).

A simple nonrelativistic model is proposed using a non-Abelian magnetic quantization approach. In this model, a deformed of the Heisenberg algebra is used. In the model, the commutator of momenta is considered proportional to the pseudo-spin. Due to the use of non-commutative algebra, a linear term in the momentum is appeared. By this model, the low-energy excitations of graphene are determined. The Landau problem is solved under a uniform magnetic field perpendicular to the plane. Then, the partition function is calculated for two branches: positive and negative. Finally, the thermal and magnetic properties of graphene are calculated. The results show that the magnetic susceptibility has a transition from paramagnetic to diamagnetic in each branch. The transition point depends on the temperature and magnetic field.

We have designed and constructed a magnet surrounding a cylindrical volume of superfluid helium-3 to isolate a region of metastable, supercooled A phase, entirely surrounded by bulk A phase - isolating the ‘bubble’ from rough surfaces that can trigger the transition to the stable B phase. We outline the design of the experimental cell and magnet and show that the performance of the magnet is consistent with simulations, including the capability to produce the high field gradient required for generating a bubble. Future plans include the investigation of possible intrinsic mechanisms underpinning the A-B transition, with potential implications for early-universe cosmological phase transitions.

The optical transition-edge sensor (TES) pushes the boundary on fault-tolerant photonic quantum computers and low-invasive bio-imaging systems. As these systems evolve, there is an increasing demand for using a TES array comprising many sensors, often exceeding one hundred. Critical temperature (T_c) of the TESes should be uniform to ensure that all TESes operate at the same bias point with a series-bias current. Using an ion-milling process, we fabricate new titanium-based TES arrays consisting of 40 TESes. Each TES has lateral dimensions of 15 µm (times ) 13 µm. Our microwave-multiplexing measurement with rf-SQUIDs confirms that 24 out of the 40 TESes exhibit (T_textrm{c} = (336 pm 6),textrm{mK}) uniform enough to apply the common bias. The yield is still 60%; however, this is the first report on the (T_textrm{c}) uniformity of the ion-milling-based TESes. Seven optical fibers are connected to TESes. Five out of the seven sensors show transition. They show energy resolution (0.54 le {Delta }E,(textrm{eV}) le 0.62) without FRM. The best energy resolution achieved without flux ramp modulation is 0.54 eV for a signal at 0.80 eV.

Templated porous materials like MCM-41 offer a scalable platform for studying one-dimensional quantum fluids due to their uniform structure. However, achieving true 1D helium behavior is limited by pore sizes typically larger than helium’s coherence length. Building on prior work using Ar preplating to reduce pore size and soften adsorption potentials, we propose a novel approach: preplating MCM-41 with cesium (Cs). Cs’s large atomic radius and non-wetting interaction with helium create an ideal confinement environment. Preliminary adsorption isotherms and small-angle X-ray scattering data confirm reduced pore radii, supporting the potential for realizing 1D ⁴He quantum fluids in Cs-preplated MCM-41.

The performance of the micro thermoacoustic refrigerator under the condition of weak gas degeneracy is studied, and a new analysis model for an irreversible quantum thermoacoustic refrigerator is established in this paper. Based on quantum statistics and thermodynamics theory, some important performance parameters of the thermoacoustic refrigerator such as the dimensionless cooling rate and the Coefficient of Performance (COP) are derived with the new model. Through numerical examples, the method to optimize the performance by adjusting some operation or structure parameters is given. At the same time, a new method to select the length of the regenerator is also found.

In this work, we investigate the magnetic, magnetocaloric, and hysteresis properties of the Spin-2 Blume–Capel model with second nearest neighbor interaction, which is a good candidate for exploring the magnetic properties of the compound LaMnO₃, within the mean-field approximation. The Hamiltonian considered includes exchange interactions between first and second neighbors ((J_1) and (J_2)), the crystal field D, and an external magnetic field h. Phase diagrams reveal the presence of a tricritical point separating first- and second-order transitions. The magnetization shows a second-order transition in the absence of the external magnetic field and a transition to a superparamagnetic phase for (h/J_{2} ne 0). The magnetic entropy (-Delta S_m) increases with field strength, reaching a maximum of 0.272 for (h/J_2 = 5), while the relative cooling power (RCP) increases linearly. Finally, the system exhibits complex hysteresis behavior, with one, three, or four loops depending on the physical parameters considered. These results highlight the potential of the compound (hbox {LaMnO}_3) for magnetic refrigeration applications.

Faraday rotation of Weyl fermions under uniaxial strain has been investigated in which the tight-binding Hamiltonian and Kubo approach have been employed. The influence of the strain has been considered as a change of hopping parameter. Results show that the Faraday rotation angle can be controlled by the external strain. Meanwhile, results show that the sign of the Faraday rotation can be reversed at some ranges of strain and incident light frequency.

The behavior of the thermodynamic compressibility of a trapped ultracold Fermi gas at unitarity is explored as the temperature approaches the critical temperature and the gas undergoes a phase transition to a superfluid state. This phase transition offers an opportunity to probe the microscopic underpinnings of this transition and can serve as a test of theoretical approaches. In this study, the collective behavior of the gas as it undergoes this phase transition is described using normal modes. The Pauli principle is applied “on paper” using specific normal mode assignments that are consistent with this fundamental principle. This study finds a small signature of the transition at the critical temperature in contrast to previous experimental and theoretical results.

In the process of 25% K and 12.5% P-doped BaFe₂As₂, the decrease of Fe ions height is accompanied by the suppression of antiferromagnetic order. Both K and P-doping cause an increase in the distance between Fe–As layers and a contraction of Fe–As bonds, and the contraction of Fe–As bond seems to be one of the most sensitive factors affecting antiferromagnetic suppression. It is found that the contraction of Fe–As bonds tends to be coordinated with an increase in Fe–Fe average distance to ultimately suppress antiferromagnetism to a smaller value. Similar structural changes result in K/P-doping causing Lifshitz transition (LT) and electronic topological transition (ETT). At the Fermi level, K-doping increases the density of states of Fe 3d and As 4p, while P-doping reduces these values.