Journal of Low Temperature Physics最新文献

The IV-VI compound semiconductors comprising binary and ternary tellurides exhibit an elevated effective g factor ((g_textrm{eff})) and reduced effective mass ((m^{*})) as a consequence of potent spin-orbit (s.o) interaction. In the ternary compound with magnetic impurity, the observations of high (g_textrm{eff}) and corresponding low (m^{*}) are not only attributed to s.o interaction, but also s/p-d/f hybridization. However, as compared to the exchange interaction, the s.o interaction is the strongest and most dominating in these diluted magnetic semiconductors. The strength of the s.o coupling is manifested by the presence of an elevated (g_textrm{eff}) and low (m^{*}) in the system. In this correspondence, we measure these parameters in (Pb_{1-x}Sn_{x}Te), with Sn as the non-magnetic impurity for different carriers at fixed temperature; T = 1.5K. Here, we formulate an effective equation within the framework of multi-band (vec {k}cdot vec {pi }) theory, incorporating the effect of s.o interaction and a magnetic field. We derive expressions for the (g_textrm{eff}) and (m^{*}) through Green’s function expansion method by considering the above interactions with Sn impurity and assuming the band inversion model relevant to the (Pb_{1-x}Sn_{x}Te) system. Finally, we extensively examine these parameters and their respective anisotropies in (Pb_{1-x}Sn_{x}Te) as functions of carrier concentration and impurity levels at (T=1.5 K).We introduce a remarkably high effective g factor, specifically (g_textrm{eff}=4280), for n(-Pb_{1-x}Sn_{x}Te) and (g_textrm{eff}=3680), for p(-Pb_{1-x}Sn_{x}Te). These values exhibit significant anisotropies, accompanied by correspondingly low effective masses, with (m_{c}^{*}=0.0023m_{0}) and (m_{v}^{*}=0.0024m_{0}) at (x=0.36) within the concentration range of (10^{17}) to (10^{18} {text{cm}}^{{ - 3}}). The existence of high (g_textrm{eff}) and low (m^{*}) in strongly s.o interacting systems like PbTe, and its alloy (Pb_{1-x}Sn_{x}Te) qualify them to be used in spin-orbit physics apart from the field of thermoelectronics.

The study of critical magnetic properties of La_0.9Bi_0.1MnO₃ is reported and discussed. The sample exhibits rhombohedral perovskite crystal structure with trivial lattice structural distortions, surprisingly maintaining the proper stoichiometry and composition as evidenced by energy-dispersive X-ray spectroscopy. The critical behavior observed in the magnetization measurements is studied using different models with proper data analysis attributed to the magnetic frustrations arising due to the inhomogeneities. The zero-field-cooled magnetization measurements below T < T_K exhibit frozen ferromagnetic inhomogeneous spin agglomerates. The observed low-temperature-dependent field-cooled magnetization measurement has been approximated by considering the quadratic and non-quadratic dispersion law incorporating corrections to the Bloch’s relation. The exponents like γ and β obtained from critical scaling analysis further confirms the inhomogeneities in magnetic behavior and doesn’t correspond to any of the well-known universality class such as 3D Ising, 3D Heisenberg and mean-field models.

We report on low-frequency measurements of few electrons floating on superfluid helium using a bespoke cryogenic cascode amplifier circuit built with off-the-shelf GaAs high-electron-mobility transistors (HEMTs). We integrate this circuit with a charge-coupled device (CCD) to transport the electrons on helium and characterize its performance. We show that this circuit has a signal-to-noise ratio (SNR) of (thicksim) 2(frac{e}{sqrt{Hz}}) at 102 kHz, an order of magnitude improvement from previous implementations, and provides a compelling alternative to few electron sensing with high-frequency resonators.

In the framework of an ensemble of spin-polaron quasiparticles formed owing to the strong coupling between the spins of copper ions and holes on oxygen ions in cuprate superconductors, the temperature dependences of the Hall coefficient (R_H) for undoped, lightly doped, underdoped, optimally doped and overdoped regimes are calculated. The anomalous behavior of kinetic coefficients is considered beyond the relaxation-time approximation within the multi-moment method for solving kinetic equation. Dependences (R_H(T)) calculated in the four-moment approach for noted doping regimes demonstrate the main qualitative peculiarities of the dependences found in the experiments on the Hall effect in cuprates. It is shown that change of the hopping integral of oxygen holes influences on the modification of anomalous sharp drop and change of (R_H) sign observed experimentally at low temperatures in underdoped regime.

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.

Controlling polarisation directly at low temperature is crucial for development of optical spectroscopy techniques at sub-Kelvin temperatures, for example, in a hybrid scheme where light is fed into and collected in the cryostat by fibres that are as easy to install as electrical wiring, but where distortions in the fibre need to be compensated for by discrete polarising optical components. The latter are poorly characterised at low temperatures. So we cool down polarising components from room temperature to 4 K and monitor the evolution of the polarisation properties in this range. We test a zero-order half-wave plate, a polarising beamsplitting cube and a dichroic polariser in the optical telecommunication range at 1.5 μm. We show that the polarisation is maintained at the (10^{-4}) level within the whole temperature range. This is consistent with the typical thermal contraction of optical materials. This level of precision is sufficient for many optics experiments at low temperature. We argue that these experiments will allow the design of compact fibre-based probes for cryogenic surfaces.

(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.

In viscous fluids, it is believed that a suction vortex is stable because the diffusion of the vorticity due to viscosity and the vorticity confinement due to flow toward the center are balanced. Therefore, the question of whether suction vortices are stable even in superfluidity is of academic importance. We have generated suction vortices by rotating turbines directly in low-temperature helium. However, this method has several problems; the suction flow could not be determined quantitatively, and we could not stabilize the motion of the turbine at low rotation speeds. In this study, we overcame these problems by introducing a pump using a fountain effect. The first step in this experiment was to determine the performance of the pump. Next, we applied this pump as a circulating pump for suction vortex generation. The vortex thus generated had perfect rotational symmetry as derived from elementary hydrodynamic equations, and its shape was stable in time. Therefore, we have succeeded for the first time in determining the rotational velocity field and circulation from the shape of the vortex generated by the fountain effect.

The quantum fluids and solids symposium series had its origin as a symposium in a series of symposia related to the Quantum Theory Project—a joint program between the University of Florida and Uppsala University that started in 1960. In the present manuscript, we comment on the evolution of the QFS symposium series with a focus on the early years and emphasize the sense of community that has developed over the years. The quantum fluids and solids symposium series started with a nearly total focus on ³He, particularly superfluid ³He, and then expanded to more broadly cover primarily liquid and solid aspects of ³He, ⁴He and their mixtures but also related technical developments. More recently, the various symposia have broadened further to include aspects of other fields for which research in ³He and ⁴He has provided significant input due to fundamental investigations and technical innovation. In turn, some of these fields have returned the favor and provided stimulation to the quantum fluids and solids community.