Journal of Low Temperature Physics最新文献

In this work, the magnetic and thermodynamic properties of dilute magnetic semiconductor quantum dots of cylindrical geometry are investigated. The eigenvalue of the quantum system we are considering is obtained by solving the one-electron Schrödinger equation within the framework of the effective mass approach. Then, taking into account the energy spectrum, expressions for thermodynamic quantities and magnetic susceptibility are obtained. The behavior of these expressions depending on temperature is studied using the parameters (B), (x), (R_{0}) and (L_{0}). Based on the results obtained, it is established that the average energy, free energy, heat capacity, entropy and magnetic susceptibility at low temperatures depend on the parameter (x). Also at low temperatures, when (x = 0), the average energy and free energy exhibit a linear relationship. With increasing temperature, this dependence becomes nonlinear. For (x ne 0), the dependence of the average energy and free energy on temperature is a rapidly increasing nonlinear function. In addition, when (x ne 0), magnetic susceptibility reaches a maximum at low temperatures. The peak height increases with (x) and disappears when (x = 0). The peak of magnetic susceptibility decreases as the magnetic field increases when (x ne 0) and shifts toward higher temperatures. The specific heat forms a Schottky peak at low temperatures and asymptotically approaches (C_{v} = 3k_{B}) at high temperatures.

In this paper, we investigate the interplay of Dzyaloshinskii–Moriya interaction (DMI) and uniform and staggered fields in x and z directions on entanglement in the spin-1/2 one-dimensional Heisenberg chain. We use the well-known mapping of this model on sine-Gordon theory to calculate the quantum entanglement quantifiers as von Neumann entropy and entanglement negativity, which provides a useful framework for studying the emergence of quantum correlation in this model. How the behavior of the spin velocity implies in a significant impact on energy of elementary excitations, carrying spin (S^z=pm 1/2), we get that the DMI interaction and external fields generate a large effect on behavior of the spinons energy and quantum correlation.

High-efficiency microcalorimeter arrays are required as imaging spectroscopy for X-ray microscopy in general and for astrophysics. We have developed in-house an array of Transition Edge Sensor (TES) X-ray microcalorimeters with mushroom-type absorbers which have a large area of (260,upmu hbox {m}) square with multiple support stems. Insufficient thermal conductivity may degrade the energy resolution. We construct a 3D FEM simulation with thermal conduction and electric feedback circuit of TES. Estimated physical parameters were incorporated into the simulation to reproduce the measured pulse waveforms. As a result, the effect of the large absorber on the degradation of energy resolution was small for the mushroom-type absorber TES calorimeter.

In this work, we propose a magnetic bolometer to be employed in the search of primordial B-modes in the CMB. These magnetic bolometers are an adaptation of the well-known metallic magnetic calorimeters used in particle physics. They rely on the magnetization dependence on temperature of alloys such as Au:Er and Ag:Er. In addition to the low intrinsic noise a magnetic bolometer of this nature offers, the broad and smooth temperature-dependent magnetization of metallic magnetic sensors ultimately translates to a high dynamic range and straightforward calibration. Their intrinsic noise equivalent power (NEP) is estimated to be in the range of 10–100 aW/(sqrt{(}text {Hz})). We outline here a workable design for such a detector utilizing an antenna-coupled approach and present the simulated power transfer ratio that was attained; the detector’s performance is discussed by combining this result with its responsivity.

The MIllimeter Sardinia radio Telescope Receiver based on Array of Lumped elements KIDs, MISTRAL, is a cryogenic LEKID camera, operating in the W band (({77}{-}{103,textrm{GHz}})) from the Gregorian focus of the 64-m aperture Sardinia Radio Telescope (SRT), in Italy. This instrument features a high angular resolution ((sim {12,textrm{arcsec}})) and a wide instantaneous field of view ((sim {4,textrm{arcmin}})), allowing continuum surveys of the mm-wave sky with many scientific targets, including observations of galaxy clusters via the Sunyaev–Zel’dovich effect. In May 2023, MISTRAL has been installed at SRT for the technical commissioning. In this contribution, we will describe the MISTRAL instrument focusing on the laboratory characterization of its focal plane: a (sim {400})-pixel LEKID array. We will show the optical performance of the detectors highlighting the procedure for the identification of the pixels on the focal plane, the measurements of the optical responsivity and NEP, and the estimation of the optical efficiency.

We present a method of creating high-density superconducting flexible wiring on flexible thin silicon substrates. The flexible wiring, called SOI flex, is created by depositing superconducting wiring on a silicon-on-insulator (SOI) wafer, selectively etching away the thicker silicon section handle layer, and bending the thinner silicon device layer. We show measurements of superconducting transition temperature and critical current for Mo, Nb, and Al on SOI flex. We discuss the expected advantages of SOI flex for low-temperature detector applications, as well as the role of stress and strain in bent silicon and niobium.

Lumped element kinetic inductance detector (LEKID) is a promising superconducting energy detector that will advance the search for rare physics events, for instance, double-beta decay. We focus on the application of LEKIDs in the search for double-beta decay with particular attention to (^{94})Zr. This proceeding reports the implementation of LEKID on unique material substrate, ZrO(_2) substrate. It was confirmed that it actually worked. This achievement marks a significant milestone toward realizing the search of rare physics events utilizing LEKIDs.

In the last years, the COSINUS (Cryogenic Observatory for SIgnals seen in Next generation Underground Searches) experiment has made significant progress both in the construction of its facility and in pursuing its physics goals: At Laboratori Nazionali del Gran Sasso (LNGS) in Italy, an underground facility was constructed, which will house experimental detectors for dark matter direct detection in a dry dilution cryostat. Construction of the main structures at the COSINUS site is finished, including the control building, the cryostat access level, and the water tank which will serve as a Cherenkov muon veto around the cryostat. With a nuclear recoil threshold of 4 keV, the latest COSINUS detector prototype approaches the design goal of 1 keV, and particle discrimination on event-by-event basis has been demonstrated. This contribution gives a brief overview on the status of COSINUS.

Fabrication of dielectrics at low temperature is required for temperature-sensitive detectors. For superconducting detectors, such as transition edge sensors and kinetic inductance detectors, AlMn is widely studied due to its variable superconducting transition temperature at different baking temperatures. Experimentally only the highest baking temperature determines AlMn transition temperature, so we need to control the wafer temperature during the whole process. In general, the highest process temperature happens during dielectric fabrication. Here, we present the cryogenic microwave performance of (hbox {Si}_{3}hbox {N}_{4}), (hbox {SiN}_{x}) and (alpha)-Si using ICPCVD at low temperature of 75 (^{circ })C. The dielectric constant, internal quality factor and TLS properties are studied using Al parallel plate resonators.