Journal of Low Temperature Physics最新文献

The decay dynamics of the (alpha)-group ((^2)D (rightarrow ^4)S transition) of N atoms stabilized in the collection of (hbox {N}_2)–Ne nanoclusters were studied at a temperature of 1.3 K. The variation of the (hbox {N}_2)/Ne ratio in nanoclusters results in substantial changes in the luminescence spectra of the (alpha)-group and in the characteristic decay times for the components of these spectra. In all obtained (alpha)-group spectra, the narrow component at (lambda) = 519.9 nm was observed. The spectroscopic results provide information about the structure of the nitrogen–neon nanoclusters. At elevated temperatures ((approx) 15–36 K), enhanced oxygen (beta)-group luminescence is observed in (hbox {N}_2)–Ne nanoclusters, with a smaller intensity enhancement than those observed within pure (hbox {N}_2) and mixed (hbox {N}_2)–Kr nanoclusters. These results confirm the energy transfer mechanism, in which excited nitrogen molecules formed on the nanocluster surface transfer energy to the stabilized oxygen atoms through the chain of (hbox {N}_2) molecules in a solid matrix.

Thermal resistance and the thermal relaxation time are important physical properties in order to cool down samples at low temperatures. In the case of a dilution refrigerator, the relation between the thermal relaxation time of working fluid in a heat exchanger and the circulation rate should be taken care of. Recently, we reported on the nanopore heat exchanger with dramatically reduced thermal resistance. Experimental results suggested that the thermal relaxation time in the sinter pad is very short (less than 1 s), while the exact value was not determined. In order to verify its relation to the circulation rate, we performed numerical simulations of the thermal relaxation time. The expected monotonic increase with decrease of temperature has been confirmed down to 50 mK. However, at lower temperatures unexpected decrease is found. This unusual behavior is considered due to relatively small thermal resistance of liquid helium compared with the thermal boundary resistance.

Superconducting transition-edge sensor (TES) is one of the sensitive single-photon detectors and possesses the photon-number resolving ability. Almost all of the existing sensitive radiation thermal absorption thin films for the generation of TESs are usually generated by optimizing the material components of the films. Alternatively, in this paper we experimentally demonstrated a flexible and controllable approach to generate the temperature-sensitive superconducting one-component thin film, by using the laser drilling technique. Specifically, we designed the sample by numerical simulation method, fabricated the aluminum (Al) thin film with the optimized pore parameters, and experimentally measured the temperature-dependent resistances in ultra-low thermal noise environments. The measured results indicate that, the resistances of the fabricated porous Al films are highly temperature-sensitive around their superconducting transition-edge regimes, and thus they can be utilized to make the desired TES devices. Although the work temperature of the prepared (mu)-Mux readout circuit does not match the generated TES configuration at present, we argue that the one-component porous films, demonstrated here, may provide an effective approach to make the desired TES device for the experimental implementation of infrared single-photon detection.

We show that the eigenvalues of the Schrödinger equation with a Coulomb potential obtained in a paper published recently in this journal do not agree with the well-known ones appearing in the literature. We also show that the authors failed to calculate the canonical partition function for that system correctly and derived meaningless thermodynamic functions that depend on the orbital quantum number.

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.