Journal of Low Temperature Physics最新文献

While closing their famous paper entitled “Pseudogap: friend or foe of high-Tc?” Norman, Pines, and Kallin underlined that before we have a microscopic theory, we must have a consistent phenomenology. This was in 2005. As it turns out in 2006, a phenomenological theory of the pseudogap state was proposed by Gor’kov and Teitel’baum. This originated from their careful analysis of the Hall effect data, and it has been very successful model as numerous investigations over the years have shown. In this mini-review, the essence of the idea of Gor’kov and Teitel’baum is presented. The pseudogap obtained by them from the Hall effect data agrees very well with that obtained from the ARPES data. This famous Gor’kov–Teitel’baum thermal activation model (in short GTTA model) not only presents a consistent phenomenology of the pseudogap state, but also rationalizes the Hall angle data, and it presents a strong case against the famous “two-relaxation times” idea of Anderson and collaborators.

We have modified the fabrication processes of metallic magnetic calorimeters (MMCs) to improve production yield. Key modifications include (i) the stress mitigation of the sputtered Nb film by optimizing the Argon deposition gas pressure, (ii) an optimized SiO(_{hbox {x}}) insulator layer fabrication by switching from a lift-off to a wet-etching method and controlling the optimizing the temperature, (iii) the joint electroplating of thick gold structures for persistent current switch leads and a thermalization layer, and (iv) a reduced sputter-deposition time of the Ag:Er sensor material by introducing a new wafer holder. These modifications contribute to increased production yield, reduced fabrication time, and enhanced overall performance. Tests on MMCs fabricated with these modifications demonstrated uniformly improved critical current of the Nb meander coils, enhanced SiO(_{hbox {x}}) insulation properties, strengthened persistent current switch systems, and reduced probability of Ag:Er oxidation. These modified MMC detectors also functioned well in tests for alpha spectrometry measurements, demonstrating good performance.

The effects of vacuum and oxygen annealing on Sr_2-xNb_xIrO₄ samples have been systematically investigated. The annealing under vacuum leads to an enhanced insulating state of the Sr_2-xNb_xIrO₄ compounds, which could be due to the evaporation of oxygen atoms which breaks the superexchange interaction between Ir and O ions. The annealing under oxygen atmosphere results in substantial straightening of the in-plane Ir–O–Ir bond and rapid depression of the canted antiferromagnetic ordering state. Importantly, the insulator-to-metal transition has been achieved by oxygen annealing of the Sr_2-xNb_xIrO₄ samples, which could be due to the enhanced hybridization of Ir 5d orbitals with the neighboring O 2p orbitals. The present results suggest that the annealing treatment could be an effective way for exploring of novel physical phenomena in Sr₂IrO₄ and related compounds.

Kinetic Inductance Detectors (KIDs) are an emerging technology useful for a wide variety of astronomy applications, including the Habitable Exoplanet Imaging Mission (HabEx), the Origins Space Telescope (OST), the Probe of Inflation and Cosmic Origins (PICO), and more. KIDs operate at cryogenic temperatures and can detect photons with high accuracy, sensitivity, and over a wide range of wavelengths. Though many KID models describe their performance well under certain operating conditions, some important pieces of physics related to quasiparticle dynamics are not yet either well understood or integrated into these models and can strongly affect device performance. In this paper we describe our framework for building an extended KID model, present the results of a quasiparticle diffusion simulation that incorporates scattering, cooling and diffusion, and discuss plans for the experimental testing of the model. We also discuss additional features to be added into future models that aim to capture a wide variety of potential scenarios encountered by researchers.

High sensitivity and low noise of superconducting quantum interference devices make them ideal for reading the minute changes in resistance of a transition-edge sensor, which occurs when it absorbs energy or power. A series of first-order gradient, cross-coupling octagonal SQUIDs specifically tailored for use in TES were developed and fabricated for the advantage of lower parasitic capacitance compared with the overlap-coupling ones. It is obtained that a lower screening parameter and increased shunt resistance per junction lead to a higher flux-to-voltage transfer coefficient. This enhancement significantly boosts detection sensitivity and effectively minimizes noise contributions from electronics operating at room temperature. The low-temperature measurement results of the sample with an input coil of 3.5 turns indicate that a small device current white noise of 4.8 pA/√Hz, a device flux white noise of 1.1 μΦ₀/√Hz, and an optimal flux-to-voltage transfer coefficient of 338.2 μV/Φ₀ are achieved. The bandwidth of a SQUID current sensor with a smaller inductance of the input coil and a larger shunt resistance exceeds 10 MHz. SQUID current sensors, featuring octagonal structures with the first-order gradient cross-coupling, exhibit low flux noise, low current noise, and a high flux-to-voltage transfer coefficient, which can satisfy the requirements of TES applications.

Erbium orthophosphate ErPO₄ was successfully prepared. The XRD pattern analyses have proved that the ErPO₄ crystallizes in the tetragonal structure (I4₁/amd). Under a magnetic field of 50 kOe, the magnetic entropy change (− ΔS_M) reaches 23.78 J/kg K at 2.6 K for ErPO₄. The value of the relative cooling power is 475 J/kg. The lowest temperature and the large MCE have inferred that ErPO₄ is a potential candidate for sub-kelvin magnetic refrigeration applications.

In this study, polycrystalline samples of Pr₂Mn₂O₆ (parent phase) and Pr_1.5A_0.5Mn₂O₆ (A = Mg, Ba) were prepared using the high-temperature solid-phase reaction method. The effects of Mg and Ba doping on magnetocaloric properties and critical behavior of the parent phase were systematically investigated. Under a magnetic field of 7 T, the relative cooling power (RCP) values of Pr₂Mn₂O₆, Pr_1.5Mg_0.5Mn₂O₆, and Pr_1.5Ba_0.5Mn₂O₆ were approximately 483.46 J·kg⁻¹, 428.22 J·kg⁻¹, and 479.88 J·kg⁻¹, respectively. The critical behavior analysis revealed that the parent phase showed short-range exchange interactions, while Pr_1.5A_0.5Mn₂O₆ (A = Mg, Ba) exhibited long-range exchange interactions. The temperature dependence of the order parameter n was studied under different magnetic fields, confirming the phase transition types and validating the accuracy of the critical exponents obtained. The research findings suggest that both the parent phase and Ba-doped ceramics at the A-site hold promise as magnetic refrigeration materials.

Cryogenic microcalorimeters are key tools for high-resolution X-ray spectroscopy due to their excellent energy resolution and quantum efficiency close to 100%. Multiple types of microcalorimeters exist, some of which have already proven outstanding performance. Nevertheless, they cannot yet compete with cutting-edge grating or crystal spectrometers. For this reason, novel microcalorimeter concepts are continuously developed. One such concept is based on the strong temperature dependence of the magnetic penetration depth of a superconductor operated close to its transition temperature. This so-called (lambda)-SQUID provides an in-situ tunable gain and promises to reach sub-eV energy resolution. Here, we present some design considerations with respect to the optimization of such a detector that are derived by analytic means. We particularly show that for this detector concept the heat capacity of the sensor should match the heat capacity of the absorber.

The Center for Axion and Precision Physics Research at the Institute for Basic Science in Republic of Korea is home to multiple active axion search experiments using cavity haloscopes that operate within the frequency range of 1–6 GHz. The haloscopes convert axions to photons, resulting in an output power of about 10({^{-24}})–10({^{-22}}) W. To detect such a small signal amidst noise, quantum-limited noise amplifiers and ultra-low-temperature environment (a few tenths of mK) are required for all critical readout components to minimize noise from all active and passive lossy components. Our primary objective is to achieve the highest possible scanning-frequency speed, which includes the time for maintenance and system calibration. This paper presents the development and operation of low-noise amplifiers for haloscope experiments targeting different frequency ranges and provides design, operational, and performance details of the amplifiers.