Journal of Low Temperature Physics最新文献

As the spatial dimension is lowered, locally stabilizing interactions are reduced, leading to the emergence of strongly fluctuating phases of matter without classical analogues. Realizing 1D platforms has been elusive, due to their inherent lack of stability, with a few notable exceptions such as spin chains and ultracold low-density gasses. The inability of such systems to exhibit long range order is essential to their universal description in terms of the Tomonaga-Luttinger liquid theory. Here we report on the experimental observation of a one-dimensional quantum liquid of (^4)He using nanoengineering to confine it within a porous material preplated with a noble gas to enhance dimensional reduction. The resulting excitations of the confined (^4)He, confirmed by neutron scattering, are qualitatively different than three- and two-dimensional superfluid helium, and consistent with Quantum Monte Carlo calculations. The results can be analyzed in terms of a mobile impurity in an otherwise linear Luttinger liquid allowing for the extraction of the microscopic parameters describing the emergent quantum liquid.

We developed a tunnel diode oscillator and characterized its performance, demonstrating its potential applications in the quantum state readout of electrons in semiconductors and electrons on liquid helium. This cryogenic microwave source demonstrates significant scalability potential for large-scale qubit readout systems due to its compact design and low-power consumption of only 1 µW, making it suitable for integration on the 10 mK stage of a dilution refrigerator. The tunnel diode oscillator exhibits superior amplitude stability compared to commercial microwave sources. The output frequency is centered around 140 MHz, commonly used for qubit readout of electrons in semiconductors, with a frequency tunability of 10 MHz achieved using a varactor diode. Furthermore, the phase noise was significantly improved by replacing the commercially available voltage source with a lead-acid battery, achieving a measured phase noise of (-)115 dBc/Hz at a 1 MHz offset.

The double-layered manganite ({La}_{1.2}{Gd}_{0.2}{Ca}_{1.2}{Sr}_{0.4}{Mn}_{2}{O}_{7}) was prepared by the solid-state reaction route, and its structural, microstructural, magnetic, electrical, and magnetotransport properties were investigated. Rietveld refinement analysis of the X-ray diffractogram shows that the structure is indexed in a tetragonal structure with an I4/mmm space group with an impurity phase. The microstructure was examined using scanning electron microscopy. The purity of the sample was examined by the energy-dispersive X-ray spectroscopy investigation. In the context of magnetic measurements, inverse susceptibility, hysteresis loop, and the magnetic behavior of the compound are discussed in detail. The sample displays a phase transition from ferromagnetic (FM) to paramagnetic (PM) at ({T}_{C}), which is equal to 290.13 K. Additionally a Griffith phase (GP) was identified and was found to be 339 K. The sample can be thought of as spin-glass-like since a significant divergence was observed at low temperatures between the magnetization curves M (T) in the zero-field cooling (ZFC) and in the field cooling (FC) modes. The electrical resistivity under an applied magnetic field of 1 T exhibits a metal–insulator transition (({T}_{MI})) at 152.98 K. The magnetoresistance was observed to decrease with increasing temperature, peaking at 23% at 11 K. The electrical resistivity in the ferromagnetic region ((T < T_{MI})) has been found to be a combination of residual resistivity and resistivities due to the weak localization, and to the electron–electron, while the adiabatic small polaron and variable range hopping models may be used to explain the resistivity data at high temperature in paramagnetic region ((T> T_{MI})).

A simple nonrelativistic model is introduced based on the deformed of the Heisenberg algebra. In this model, the commutator of momenta is proposed proportional to the pseudospin. The low-energy excitations of graphene are derived by using this model. The Landau problem has been solved by taking into account a uniform magnetic field perpendicular to the plane. Then, the Tsallis non-additive formalism is employed to obtain the probability and the partition function for two branches, the positive and negative. Finally, the magnetic susceptibility and thermodynamic properties of graphene are determined. The findings reveal that the magnetic susceptibility has a positive value and shows a paramagnetic behavior in each branch. The susceptibility in the negative branch has a lower value in comparison to the positive branch for any values of non-extensive parameter. The specific heat displays a peak structure. For a given non-extensive parameter, the peak position of the specific heat occurs at a particular temperature in each branch. The results show that both parameters, temperature and non-extensive parameter, have important roles in magnetic susceptibility and thermal properties of the system.

Electrons trapped on the surface of liquid helium is an extremely clean system which holds promise for a scalable qubit platform. However, the superfluid surface is not free from fluctuations which might cause the decay and dephasing of the electron’s quantized states. Understanding and mitigating these fluctuations is essential for the advancement of electrons-on-helium qubit technology. Some work has been recently done to investigate surface oscillations due to the mechanical vibration of the cryostat using a superconducting coplanar waveguide resonator. In the present work, we focus on a sub-hertz frequency range and observe a strong effect of surface oscillations on the temporal dynamics of the Rydberg transition of electrons confined in a microchannel trapping device. We suggest possible origin of such oscillations and find a reasonable agreement between the corresponding estimation of the oscillation frequency and the observed result.

The MIllimeter Sardinia radio Telescope Receiver based on Array of Lumped elements (MISTRAL) KIDs is a millimeter camera operating at 90GHz that was recently installed on the Sardinia Radio Telescope (SRT) as part of the SRT-HighFreq program, which aims to expand the capabilities of the radio telescope up to the W-band. After technical and scientific commissioning (2023–2024), MISTRAL will be open to proposals from scientists as a facility instrument. MISTRAL provides a wide 4’ field of view, sampled at a resolution of 12” with approximately 400 kinetic inductance detectors. The sky in the W-band is well explored by CMB experiments; however, their resolution is limited to about 1’. Using large single-dish radio telescopes like SRT or the Green Bank Telescope allows to probe angular scales down to 10–12”, allowing scientists to obtain new data and complementary information in multiple scientific cases. In this contribution, we will review observational perspectives and performance forecasts of MISTRAL, based on laboratory measurements of the noise properties, for selected scientific cases such as galactic science and high-resolution measurements of the Sunyaev–Zel’Dovich effect in galaxy clusters and in the cosmic web.

In this study, we investigate the behavior of non-relativistic quantum particles interacting with a modified Pöschl-Teller potential in the backdrop of a topological defect created by global monopoles. We derive the radial equation of the Schrödinger wave equation through a wave function ansatz and obtain an approximate (ell ne 0)-state eigenvalue solution by employing the Nikiforov-Uvarov method. Our analysis demonstrates that the presence of a global monopole affects both the energy eigenvalue and the wave functions of non-relativistic quantum particles, deviating from the behavior observed in flat space with this potential. Furthermore, we calculate the Shannon entropy for this quantum system and evaluate how the existence of the topological defect and potential influences it.

In this work an overview is given on experiments with surface electrons above the quantum solids hydrogen and neon. While two-dimensional ensembles of surface electrons on the quantum liquid superfluid helium have been studied already in great detail, investigations of electrons on quantum solids are rather sparse. Since recently electron-on-neon qubits have been shown to exhibit very long coherence times, there is a demand for understanding the conditions for a successful growth of thin solid neon films as a qubit substrate. Therefore, in this review also the triple point wetting phenomenon of the hydrogen isotopes and neon is discussed, which dominates the growth of solid films of these materials.

The influence of nonstoichiometry on the structural and magnetic properties of (hbox {Sr}_2hbox {FeMoO}_6) (SFMO) has been investigated by varying the ratio of Fe in polycrystalline samples. We demonstrate that changes in the Fe/Mo ratio can elevate the Curie temperature ((T_textrm{C})) in SFMO, even though the total magnetic moment is reduced at the same time. The discoveries of the stoichiometric imbalance between the cations Fe and Mo are discussed in the context of first-principles calculations on the electronic and magnetic structures of SFMO using the GGA+U method. Our theoretical results reveal that Fe deficiency reduces the (T_textrm{C}) due to the antiparallel alignment of Fe moments in Mo positions, which is consistent with experimental observations. In contrast, accurate (T_textrm{C}) trends for Fe excess are reproduced only by considering spin disorder, with both parallel and antiparallel Fe moment orientations. These insights provide a detailed understanding of the magnetic interactions in SFMO. Our findings lay the groundwork for developing innovative SFMO-based materials and emphasize the significance of stoichiometry control in optimizing SFMO properties.

Liquid helium cryogenic system is crucial for achieving low-temperature superconductivity in particle accelerator and controllable nuclear fusion devices. However, the heat conductivity of copper in the 4K region is 400–800 W m⁻¹ K⁻¹, which limits the performance of superconductivity system. The application of helium-based oscillating heat pipe (OHP) promotes this deficiency mitigation, with a maximum effective thermal conductivity (ETC) ranging from 4000 to 16,000 W m⁻¹ K⁻¹. Although numerous scholars have experimentally observed the maximum efficiency point of OHP, but its underlying mechanism remains unclear. In this study, a test rig for measuring the heat transfer performance and dynamic parameters of helium-based OHP in the 4K region was constructed. A numerical simulation method for the gas–liquid two-phase unsteady flow process in the OHP was established. The amplitude and period distribution of dynamic pressure fluctuations in OHP were analyzed. The correlation between its pressure fluctuations and heat transfer process was explored. Finally, the mechanism of the maximum efficiency point was revealed with the oscillating characteristics for helium-based OHP in the 4K region.