bluuebunny/crossref_metadata_2025 huggingface dataset:
Current-conduction states in granular media
Authors: Shekhter R. I. , Kulik I. O.
Published: November 2024

A study is made of the current-conduction states in three-dimensional granular media, assuming that charge transfer occurs by a mechanism of electron tunneling between the granules and is limited by effects connected with the discrete nature of each electric charge. In the low-voltage range the conductivity has an activated nature σ∼σηexp(−T0/T), where T0= e2C is the characteristic activation energy, C being the capacitance of a granule. In the limiting cases T≫T0 and T≪T0, the calculation of the conductivity reduces to the solution of the problem of a charge carrier’s random “walking” or migration throughout the granulated material. The main contribution to σ is from walks over separate paths .of easiest passage (percolation paths). For T/T0≫1, the conductivity does not depend on temperature. In the inverse case T/T0≪1 a characteristic activation exponent appears. In the extreme low-temperature range T≪(a/d)T0 (a is the interatomic spacing and d is the mean distance between granules), the temperature dependence of the conductivity becomes more complicated and there must be a transition to the Mott law σ∼exp[(−T*/T)1/4] characteristic of hopping conduction over localized impurity states in doped or amorphous semiconductors.
Towards a theory of the Tomasch effect in SINS junctions
Authors: Bezuglii A. I. , Mitsai Yu. N.
Published: November 2024

Current states in SINS junctions are investigated for non-zero voltages across the junction. The features of the volt-current characteristics of the junction are examined, which are determined by the presence of discrete energy levels of quasi-particles within the normal interlayer.
Breakdown of a uniform superfluid flux near the absolute instability boundary
Authors: Shumeiko V. S.
Published: November 2024

The hydrodynamic instability of a uniform superfluid flux is considered at the absolute instability boundary. A model equation describing the nonlinear evolution of the destructive fluctuations at temperatures near zero is obtained. The maximum dimensions of the stable normal domains formed during the development of the hydrodynamic instability, and the possibility of the generation of quantized vortices of the superfluid velocity field therein are investigated.
Self-trapped states of surface electrons over a helium film
Authors: Monarkha Yu. P.
Published: November 2024

Surface electron states over a helium film on a solid substrate are investigated. It is shown that the image forces acting on the electron from the substrate can result in electron localization along the liquid-vapor interface because of deformation of the helium surface. The binding energy, effective mass and mobility of these entities are calculated. Galvomagnetic phenomena in a surface electron gas are studied in detail taking account of the deformation of the helium surface under the localized electron.
Experimental investigation of a doppleron in molybdenum
Authors: Galkin A. A. , Tsymbal L. T. , Cherkasov A. N. , Vitebskii I. M.
Published: November 2024

A doppleron in molybdenum due. to carriers of a hole octahedron near the cross section with extremal value δ S/δ kH was investigated experimentally. It was found that 1/2π(δ S/δkH)ext = (0.514 ± 0.005)Å−1. The indicated doppleron had not been observed before.
Implications of vacancy formation entropy
Authors: Hetherington J. H.
Published: November 2024

Knowledge of vacancy formation entropy in solid He will lead to some information about vacancy structure. Finite vacancy bandwidth gives a negative contribution to vacancy entropy. Positive contributions to vacancy entropy come from excited states of the vacancy, either in the form of localized phonon modes, or in more complex structure changing excited states.
Nuclear spin conversion and low-temperature phase transitions in solid CH4
Authors: Krupskii I. N. , Prokhvatilov A. I. , Gasan V. M.
Published: November 2024

Results of x-ray diffraction studies on solid methane in the range 6 to 24°K are reported. Measurements, of temperature variations of the lattice parameter have revealed, along with the well-known phase transition at 20.49°K, volume jumps of 0.15 and 0.12% at 9.9 and 18.0°K, respectively, in samples which were equilibrium as concerns composition of spin modifications (ortho, para, and meta). The two phase transitions are shown to be similar in nature, namely, are caused by complete orientational ordering of the molecules. However, in each case the ordered state exists within a limited temperature range and as the temperature T is lowered, the concentration of metamodification (S = 2, the lower permitted rotational level of the molecules corresponds to J = 0) grows and as a result, the state becomes disordered, partly or completely. A possibility of such quantum-mechanical disordering was predicted for crystalline methane in a number of theoretical papers.
Second-order self-consistent phonon theories
Authors: Kanney L. B. , Horton G. K.
Published: November 2024

In this paper we study the second order equations of self-consistent phonon theory, in the high temperature limit. The model we examine assumes (12−6) Mie-Lennard-Jones forces between nearest neighbors only. If we chose potential parameters appropriate for solid Ar, we find no self-consistent solutions of the equations. For potential parameters appropriate for solid Xe, solutions for the second order self-consistent equations exist up to about 80°K only. In this case we calculate the specific heat at constant volume and find very large corrections to the renormalized harmonic approximation and to the Improved Self-Consistent Phonon Theory. We conjecture that the linked cluster expansion of Choquard diverges and that his second order theory has no useful range of convergence. Alternative formulations of self-consistent phonon theory, such as Horner’s may avoid these problems.
Neutron diffraction studies of deuterium solid structures and transitions
Authors: Yarnell J. L. , Mills R. L. , Schuch A. F.
Published: November 2024

Fine-grained, randomly-oriented samples of solid D2 were prepared by injecting D2 gas into liquid He at 4°K. Para (J = 1) concentration of 2%, 29%, and 96% were used. In all cases, the as-frozen solid was predominantly fee, with 10% of the material in the hep form expected at 4°K. Upon annealing at 12°K, all samples transformed to pure hep, and remained hep when returned to 4°K. As expected, only the 96% para samples transformed to a cubic phase with cooling to 1.5 °K. However, the transition did not go to completion and neither holding for many hours at 1.5°K nor cycling between 1.5°K and 4°K would make it do so. This behavior confirms earlier observations that the transition is martensitic. Careful analysis of the data, using cross-correlation techniques, revealed the presence of very weak, mixed-index peaks characteristic of the ordered Pa3 structure. Evidence of stacking faults (peak broadening and, for fcc, peak shifts) was seen for all structures. The average number of planes between faults was 14 for the as-frozen fcc, 95 for the annealed hep, and 27 for the Pa3. At 4°K, the molar volumes of the as-frozen fcc and the annnealed hep were the same within the experimental accuracy, and there was no observable volume change when the 2% and 29% para hep samples were cooled from 4°K to 1.5°K. These molar volumes are given by V = 19.998—0.203x ± 0.013 cm3/mol, where x is the para-concentration. The molar volume for the Pa3 at 1.5 °K was 19.681 ± 0.007 cm3/mol, with x =0.96. For the annealed hep, the c/a ratio was smaller than ideal by 1 part in 1200. For all structures, the observed intensities of the diffraction peaks were in good agreement with calculations based on wave functions for free D2 molecules in the J = O and J = 1 rotational states.
Inelastic neutron scattering from hydrogen
Authors: Nielsen M. , Ellenson W. , Shapiro S. , Carneiro K.
Published: November 2024

Neutron scattering results are presented for solid hydrogen and for molecular hydrogen absorbed as monolayers on grafoil. The lattice dynamics of solid hydrogen have been studied by coherent scattering from single crystals and by incoherent scattering from polycrystalline hydrogen under pressure. From the first kind of experiments we find the phonon dispersion relations and from the second kind of experiment we have determined the Debye-Waller factor at different densities. No other crystalline phases than the hep phase have been found at any temperature in the solid phase at pressures up to 1800 bar. Monolayers of hydrogen abosorbed in grafoil have been studied by incoherent scattering where paramolecules are converted to orthomolecules. The main conclusion from these scattering experiments is that the conversion line at 14.6 meV is narrow, the width being smaller than 0.2 meV, and that we can observe this narrow line up to near 40 °K where the intensity disappears. The variation of the intensity of this line with the scattering vector is similar to that observed for molecules in solid hydrogen at pressures up to about 1600 bar.
Excess energy of mixing of hydrogen-deuterium solutions
Authors: Karnatsevich L. V. , Bereznyak N. G. , Bogoyavlenskii I. V.
Published: November 2024

The complete constitution diagram of vapor-liquid-crystal solutions of hydrogen and deuterium is investigated experimentally in the temperature region from 14°K to 20°K. On the basis of the data obtained, the excess energy of mixing is calculated in the solid phase along the melting diagram. The presence of a positive excess energy corresponds to the fact that below the critical temperature Tk, separation of solutions is thermodynamically advantageous. The results of calculations of the excess energy of miring and Tk are found in good agreement with theoretical computations in Prigogine’s model and according to Nosąnow’s theory of quantum crystals.
Influence of the impurities on the thermal properties of solid parahydrogen
Authors: Manzhelii V. G. , Chausov G. P. , Popov V. A. , Vladimirova L. I. , Tolkachev A. M. , Alfxandrovskii A. N.
Published: November 2024

At low temperatures, impurities influence strongly heat capacity and thermal conductivity of a crystal when the molecular parameters of the impurity differ substantially from those of the solvent. Relevant calculations and measurements are available only for crystals that are described consistently within the framework of the harmonic approximation. This paper presents studies of the effect of heavy impurities (neon) on thermal conductivity of the quantum crystal of parahydrogen at temperatures 2 to 12 °K and impurity contents 2.04 and 0.53 mole % Ne. Below 6°K, a strong impurity-induced anomaly in heat capacity has been observed, its magnitude exceeding that predicted by the harmonic theory. The effect of ortho-impurities on the thermal expansion of parahydrogen was studied in the 2—7°K range in order to understand the role of impurities of different ground-state molecular symmetry.
Further experiments on the new phases of He3
Authors: Lee D. M.
Published: November 2024

Recent measurements of sound attenuation and nuclear magnetic resonance phenomena in superfluid He3 are discussed. Strong evidence for the anisotropy of A He3 is presented. Measurements along the melting curve leading to evidence for the new phases of liquid and solid He3 are discussed.
Effect of impurities on the Josephson current through SNS junctions
Authors: Kulik I. O. , Mitsai Yu. N.
Published: November 2024

The effect of impurities on the steady-state Josephson current through a superconductor—normal metal—superconductor junction is analyzed. It is shown that, when ξ0≪l∼d (l denoting mean free path length and d denoting the thickness of the normal metal layer), impurities cause an appreciable decrease in the current and a change in the form of its dependence on the phase. The dependence of the critical current for weak-superconduction current on the thickness of the normal metal layer is found to be of the form jc∼j0e−d/ζ with ζ denoting the effective coherence length and defined as the reciprocal of ζ−1=2πT/ℏvo/+1/l.
The spin wave damping coefficient in helical magnetic structures
Authors: Bar’yakhtar V. G. , Stefanovskii E. P. , Yablonskii D. A.
Published: November 2024

The spectrum and damping coefficient of spin waves in magnets with helical magnetic structures, arising from the Dzyaloshinskii type of interaction, are studied. It is shown that the spectrum for such a structure is linear in a region of small wave vectors while the damping coefficient is proportional to the square of the wave vector. The treatment is carried out by quantization of the classical Landau-Lifshitz equations of motion for the magnetic moment.
Spectroscopic studies of the phase transition in (NH4)2BeF4
Authors: Popkov Yu. A. , Shabanov V. F. , Eremenko V. V. , Aleksandrov K. S.
Published: November 2024

Raman spectra of ammonium fluorine beryllate were studied in the temperature range 4.2−300 °K. Normal lattice vibration frequencies were determined and identified. In the frequency range 35−550 cm−1 external lattice vibrations and vibrations of the group BeF4−− were found. Internal NH4+ ion vibrations have lines in the frequency range 1410−1480 cm−1, 1650−1740 cm−1, and 3050−3330 cm−1 close to the vibration frequencies of the free ammonium group. In a detailed study of the temperature dependence of low frequency Raman spectra in the region of the ferroelectric phase transition (TC= 176 °K) anomalous behavior was observed in several spectral lines. Sharp changes in frequency, half-width, and intensities were observed. In studying B2 type vibrations a nonlinear resonance between vibrations at 82 and 58 cm−1 was found (4.2 °K). With increase in temperature the lines approach each other, collapsing in the region of the Curie point. It is proposed that this nonlinear interaction may be the cause of the phase transition.
Surface charges in helium (a survey)
Authors: Shikin V. B. , Monarkha Yu. P.
Published: November 2024

A survey is made of theoretical and experimental results obtained so far pertaining to the characteristics of surface charges at the helium liquid-vapor interphase boundary. The electron states above a plane helium surface are described; the theory of interaction between surface electrons and thermal surface excitations in liquid helium is presented, as is also the theory of self-localized electron states (surface anions) resulting from a deformation of the liquid-vapor interface; the discussion covers also a series of phenomena associated with the Wigner crystallization of a gas of surface electrons into a two-dimensional periodic lattice; and behavior characteristics of heavy ions in liquid helium near the liquid-vapor interface are discussed too.
Low-temperature magnetic behavior of gadolinium ortho-ferrite and certain of its substitution compounds
Authors: Derkachenko V. N. , Kadomtseva A. M. , Ovchinnikova T. L. , Timofeeva V. A. , Khokhlov V. A.
Published: November 2024

The rotational moments of gadolinium ortho-ferrite were measured in different crystallographic planes at 2.1°K. The rotation diagrams obtained indicate the presence of a magnetic ordering of the spins of the Gd3+ ions along the a axis of the crystal. A “flipping” of the Gd3+ antiferromagnetic sublattices was observed with the application of a magnetic field of ∼ 104 Oe along the a axis of the rhombic crystal. It is assumed that monoclinic distortions of the lattice occur during the ordering of the Gd3+ ions. The magnetization of GdFeO3, GdAl0.1Fe0.9O3 and GdGa0.1Fe0.9O3 were measured over the 4.2–80°K temperature range. It is shown that the spontaneous moment of the iron ions changes little with the partial substitution of Fe3+ ions by Ga3+ and Al3+ ions, while the effective field acting on the rare-earth ions, caused by the iron ions, increases. The possible cause of this phenomenon is discussed.
Intermediate state of ferro- and antiferromagnets and absorption of ultrasound
Authors: Popov V. A.
Published: November 2024

It is shown that the dependence of the phase concentration on the sound pressure results in an abrupt growth of ultrasound absorption in the intermediate state of antiferromagnets in proportion to ω2He2/HA2 (He and HA are the exchange field and the field of magnetic anisotropy, and ω is the ultrasound frequency). This absorption is considerably more intensive than the ultrasound absorption due to phononphonon and phonon-magnon collisions, as well as that related to the mechanism proposed by Bar’yakhtar and Ivanov.
Surface impedance of a metal plate with specular boundaries in a parallel magnetic field
Authors: Kaner É. A. , Makarov N. M. , Rozhavskii A. S.
Published: November 2024

A theory of the geometrical dimensional effect and resonance phenomena in a plane-parallel plate sited in a permanent and homogeneous magnetic field H parallel to the boundary of the metal is developed. Assuming a quadratic and isotropic dispersion law for the electrons (alkali metal), exact equations are obtained for the high-frequency conductivity tensor of a plate with specular boundaries. The surface impedance is calculated in the case of unilateral excitation of the electromagnetic field in the specimen. A study is made of the dependence of this impedance on the frequency of the external wave ω, the thickness of the plate d, and other parameters in a wide range of variation of the magnitude of the magnetic field H. The investigation is carried out under conditions of the anomalous skin effect.
Absorption spectrum of crystalline RbMnCl3
Authors: Popkov Yu. A. , Beznosikov B. V.
Published: November 2024

The optical absorption spectrum of crystalline RbMnCl3 (TN = 94°K; spatial group  D6h4) is studied at temperatures of 4.2–40°K and magnetic fields of 0–300 kOe. In the neighborhood of the 6A1g(6S5/2)→A1g,4Eg(4G) transition of the Mn2+ ion all the absorption bands for zero field are of electric dipole nature. This follows from the symmetry properties of the crystal, namely, the presence of manganese ions shifted off the inversion center. The intensity of the spectral bands is found to depend on the mutual orientation of the electric vector of the light and the magnetic moments of the sublattices. Exciton-magnon transitions are observed due both to excitation of magnons and to their absorption (“cold” and “hot” exciton-magnon satellites), and the frequencies of the short wavelength magnons which contribute to the absorption spectrum are found to be about 40–75 cm–1. The latter value agrees with the estimates obtained here. In an external magnetic field it is found that there is a nonlinear shift of the bands and that new bands appear with intensities proportional to the square of the field. The polarization of two of the bands has a magnetic dipole nature. The behavior of the absorption bands in a magnetic field is discussed in terms of magnetic Davydov splitting.
Ultrasonic examination of the elastic characteristics of crystalline β-oxygen
Authors: Bezuglyi P. A. , Tarasenko L. M.
Published: November 2024

The adiabatic compressibility and the Poisson ratio of solid β-oxygen over the 36–43°K temperature range are determined from measurements of the velocity of longitudinal and transverse ultrasonic waves. Determined also are the isothermal elastic constants, the Gruneisen coefficients, and the Debye temperature. The temperature dependence of the isothermal compressibility is compared with theoretical data.
The constant-volume thermal conductivity of liquid and gaseous nitrogen over the 64.2–300°K temperature range. Thermal conductivity of nitrogen in the critical region
Authors: Slyusar’ V. P. , Tret’yakov V. M. , Rudenko N. S.
Published: November 2024

An experimental study was made of the constant-volume thermal conductivity of nitrogen over the 64.2–300°K temperature range, including the critical region. The density of nitrogen varied from 0.067 to 0.864 g/cm3. The results of measurements are compared here with those obtained by other authors and with Enskog’s theory. Within the critical range estimates are made of the critical exponent for the thermal conductivity of the liquid phase (a'L =0.7±0.05) and of the vapor phase (a'v = 0.7±0.05) as well as on the critical isochore (a = 0.76±0.1). The value a'L = a'V = a≃2/3 according to theory, is thus confirmed within given accuracy limits.
The P-ρ-T relations and the equation of state of nitrogen in a wide region around the critical point
Authors: Zozulya V. N. , Blagoi Yu. P.
Published: November 2024

The P-ρ-T relations have been investigated in nitrogen near the critical point. Information has been obtained about the asymptotic laws (the values of the critical exponents β, δ, γ, γ’ and the coefficients in the power law dependences have been determined), and corrections to them have been obtained away from the critical point. The results confirm the asymptotic symmetry of the thermodynamic properties with respect to the phase transition point. The “linear model” of the scaling-law equation of state has been shown to be valid in a wide region around the critical point of nitrogen.
The effect of impurities on the residual electrical resistivity of thallium
Authors: Dukin V. V. , Aleksandrov Β. N. , Dalakova N. V.
Published: November 2024

The effects of twelve impurities (Te, Sb, Bi, As, Ag, Mg, Cd, Sn, Pb, Hg, In, and Zn) on the residual resistivity (ρ0) of thallium have been studied. The thallium used was ≥ 99.999% pure with a resistance ratio δ0 = ρ0/ρ293 = 3.5 × 10–5, and the alloys were prepared in the concentration range from 1 × 10–3 to 2 wt.% with subsequent homogenization by annealing in a pure helium atmosphere. The values found for the change in residual resistance of thallium (Δρ0/c) upon dissolution of 1 at .% of impurity depend quadratically on the valence difference between impurity and host (Δ z) for the group V and VI impurities. Calculations of Δρ0/c have been carried out using phase shifts, using the form factors of Appapillai found from first principles, and using the Ashcroft model pseudopotential which showed that the latter case gives the best agreement with experiment (discrepancy no more than a factor of 2) with ∼0.5 conduction electrons per atom.
Critical currents in superconducting bridges of variable thickness
Authors: Lapir G. M. , Likharev Κ. K. , Maslova L. A. , Semenov V. K.
Published: November 2024

The influence of a number of factors on the steady-state properties of variable-thickness bridges, in particular on the current and phase distribution across the bridge and the critical current Ic, are theoretically examined. These factors include the width of the bridge W, the shape of the banks, and of the applied magnetic field. An expression is found for the characteristic size δJ of current variation across the bridge. The Ic(IH) characteristics, where IH is the current generating the applied magnetic field, are calculated. Dependences of the coefficient G=|dIc/dIH|Ic=IH on the bridge parameters are presented.
Surface impedance in the mixed state and surface superconductivity in niobium
Authors: Krylov I. P. , Konyukhov A. A.
Published: November 2024

Radio frequency range measurements of the imaginary component of surface impedance were made in pure niobium specimens in the mixed state and in the surface superconductivity regime at liquid helium temperatures with various orientations of the constant external magnetic field relative to the specimen surface and varying high-frequency current direction. Anisotropy in the critical fields was measured and their temperature dependence was determined. Penetration of the high-frequency field into the interior of the superconductor in the mixed state was described approximately with the aid of a simple model in terms of a complex conductivity and a high-frequency magnetic permeability. Within the framework of this simple model of the superconductive layer the surface density of superconducting electrons was obtained from experimental impedance data, and it was shown that this value decreases sharply in an inclined field. Impedance hysteresis was observed in the surface superconductivity region.
Exciton-magnon absorption of light in crystals near the magnetic ordering point
Authors: Shapiro V. V. , Litvinenko Yu. G.
Published: November 2024

The dependence of the frequencies of exciton and exciton-magnon light absorption in antiferromagnetic FeF2 is investigated over a broad temperature range (from 4.2 to 300°K) and in magnetic fields up to 220 kOe. “Hot” magnon satellites of the exciton line have been detected which correspond to transitions involving the absorption of either one or three magnons. The substantially different behavior of the exciton- magnon band frequencies in the neighborhood of T = 78.4°K is explained by the significant decrease in the energy of the spin wave appearing in different combinations in the energy of “cold” and “hot” magnon satellites. At temperatures near TN, the application of a magnetic field oriented along a fourfold crystallographic axis produces variations in the FeF2 spectrum which are identical to those caused by a decrease in the Néel temperature.
Localized states of Bose defects
Authors: Dolgov A. S.
Published: November 2024

Energies of state of interacting quantum defects obeying Bose-Einstein statistics are calculated close to fixed imperfections of the crystal lattice.
Phonon-libron interaction and thermal conductivity in the simplest molecular crystals
Authors: Manzhelii V. G. , Kokshenev V. B. , Koloskova L. A. , Krupskii I. N.
Published: November 2024

The thermal conductivity of solid N2, CO, N2O, and CO2 is studied experimentally and theoretically. Experimental studies were performed over the following temperature ranges: N2, 23–55°; CO, 23–58°; N2O, 24–120°; and CO2, 27–123°K. The effect of small angular oscillations of the molecules (librations) on the heat transfer process is considered. It is shown that the basic mechanism determining thermal resistance in these crystals in the high temperature range (T>ΘD/4) is phonon scattering by the libron subsystem. A collision integral is constructed for the description of the phonon-libron interaction processes with consideration of one-and two-libron-phonon scattering processes. Good agreement was obtained between calculated and experimental values of the coefficient of thermal conductivity.
Influence of the superconducting transition on the creep of high-purity tin single crystals
Authors: Soldatov V. P. , Startsev V. I. , Shklyarevskaya G. I.
Published: November 2024

The creep of tin single crystals is investigated in the 1.6–3.7°K range and the influence of the superconducting transition is studied. The creep curves are described by a logarithmic law. The temperature and strain dependence of the enhanced plasticity effect are studied, and the stagelike nature of the latter is shown. Good agreement is obtained between experimental results and the predictions of the fluctuation theory of plasticity enhancement.
Elementary excitations of α oxygen (review)
Authors: Gaĭdideĭ Yu. B. , Loktev V. M. , Prikhot’ko A. F. , Shanskiĭ L I.
Published: November 2024

We describe the main properties of elementary excitations of the antiferromagnetic modification of solid oxygen (α oxygen), as well as their manifestations in the absorption spectrum. A theory of collective excitations of the states of α oxygen is developed. Two-quasiparticle (exciton-magnon and two-exciton) states are discussed, as well as the role of quasiparticle interactions. It is shown that exciton interaction leads to formation of bound states—biexcitons, which give rise to the doublet structure in the two-exciton absorption spectra of α oxygen.
Two-magnon absorption in a low-dimensionality antiferromagnet
Authors: Anders A. G. , Zvyagin A. I. , Pereverzev Yu. V. , Petutin A. I. , Stepanov A. A.
Published: November 2024

The antiferromagnetic resonance spectrum of the quasi-one-dimensional antiferromagnet CsMnCl3⋅2H2O in magnetic fields above the reversal field shows an additional absorption band of asymmetric shape whose intensity grows with increasing temperature and falls with increasing frequency. A mechanism for the appearance of the band is proposed, involving the excitation of threshold two-magnon absorption. It is shown that the intensity of such absorption is substantially greater in a low-dimensional magnet than in a three-dimensional one.
Plastic deformation of nickel single crystals at low temperatures
Authors: Kononenko V. I.
Published: November 2024

A study has been made of the deformation of 99.8%-nickel single crystals at temperatures from 77.3 to 1.6° K in a rate-of-straining range of 7⋅10-5 to 3.5⋅10−2sec−1. It has been shown that single crystals of nickel are characterized by an increase of τ and ϵ with a lowering of the temperature to 1.7°K, and also by the appearance of jump-like straining at helium temperatures. The change in the nature of the straining dependence is probably due to the fact that with ϵ̇∼10−2sec−1 the speed of the dislocations reaches values at which dynamic effects are manifested. Evidence of this is the sharp increase in the electrical resistance of a crystal strained to the yield point, due to point defects generated with the movement of the dislocations with jogs.
Influence of a change in the plasticity of metals and alloys during a superconducting transition on the yield point above Tc
Authors: Didenko D. A. , Pustovalov V. V.
Published: November 2024

The influence of prestraining at a temperature below Tc of superconducting lead and lead-bismuth alloy specimens in the normal and superconducting states and under a multiple repetition of the superconducting transition on the straining stress above and below Tc is studied. It is discovered that prestrain with multiple n→s transitions results in an additional rise in the yield point.
Spin-wave damping in antiferromagnets with dislocations
Authors: Bar’yakhtar V. G. , Seminozhenko V. P. , Sobolev V. L.
Published: November 2024

The interaction of spin waves with dislocations in antiferromagnets with magnetic anisotropy of the “easy plane” type is considered. Magnon damping coefficients γ(k) governed by such interaction are calculated.
Energy spectrum of impurity excitations in superfluid helium
Authors: Esel’son B. N. , Slyusarev V. A. , Sobolev V. I. , Strzhemechnyi M. A.
Published: November 2024

The experimental data on the density of the normal component in helium-isotope solutions have been used to examine the form of the Fermi branch in the elementary-excitation spectrum. It has been found that the state density for the impurity excitations of large momentum is higher than had previously been assumed, and also that these quasiparticles produce an appreciable contribution to the thermodynamic parameters. The dispersion law obtained allows one to describe with good accuracy the available experimental data on the normal density for 3He-4He solutions over wide ranges of temperatures and concentrations. It has been found that the energy spectrum of the 3He quasiparticles has a new feature—an end point, at which an impurity excitation decays into a roton and a 3He quasiparticle of small momentum.
Investigation of the physical mechanism of obtaining temperatures below 2 °K by desorption of helium
Authors: Bagatskii M. I. , Manzhelii V. G. , Minchina I. Ya. , Popov V. A.
Published: November 2024

It is shown that by using desorption of helium to obtain temperatures below 2°K one can lower the working temperature and considerably reduce the mass flow of gas as compared with the method involving pumping vapor above liquid helium. It is shown that these effects are mainly determined by the occurrence of an unsaturated superfluid helium film due to desorption.
Ground state in a nonzero moment pairing system. I. Single-particle excitation
Authors: Chechetkin V. R.
Published: November 2024

A system with nonzero moment pairing can simultaneously contain pairs with distinct arbitrary projections of the moment. Such a state is isotropic and possesses an isotropic excitation spectrum. In this paper the ψ function of the isotropic state is constructed and it is shown that the energy of the ground state is lower than in the Anderson-Morel solution. The single-particle excitation spectrum of the isotropic state coincides with the spectrum in the Gor’kov-Galitskii scheme. In the case of p-pairing, solutions with J = 1 and 2 can be constructed in addition to the isotropic solution with J = 0, which leads to a natural classification of the anisotropic solution.
Ground state in a nonzero moment pairing system. II. Collective excitations
Authors: Chechetkin V. R.
Published: November 2024

Collective excitations in the Gor'kov-Galitskii scheme are investigated. It is proved that the solutions are stable. When k = 0, excitations with ω2 = 0, 4Δ2 are accompanied by gap excitations corresponding to states with a nonzero moment of two Cooper pairs. The use of photon spherical functions in the case of triplet pairing leads to a significant simplification of the calculation.
Pressure effects for the paramagnetic susceptibility and Knight shift for AuGa2 superconducting films
Authors: Palistrant M. E. , Trifan A. T. , Gudima K. K.
Published: November 2024

Expressions have been derived for the paramagnetic susceptibility and shift in the nuclear-magnetic resonance frequencies KAu and KGa for thin superconducting films of AuGa2 under pressure. Liftshitz’s electron-transition model is employed. The pressure dependence of χ, KAu, and KGa has been calculated for zero temperature and various scattering relaxation times at the film boundary.
Critical current hysteresis in thin superconducting films
Authors: Volotskaya V. G. , Musienko L. E. , Dmitrenko I. M. , Kalekin Yu. V.
Published: November 2024

Investigations of the hysteresis of the current-voltage characteristics of thin superconducting films of tin and indium over a wide temperature range are presented. It is shown that under ideal heat transfer conditions, the hysteresis and its temperature dependence agree with the results of Shklovskii's theory according to which the hysteresis is due to superheating of the electrons relative to the lattice.
Theory of superconductivity of systems with pairing of spatially separated electrons and holes
Authors: Shevchenko S. I.
Published: November 2024

The possibility of superconductivity is predicted in systems with pairing of spatially separated electrons and holes. Gor’kov and Ginzburg-Landau equations are obtained for the systems under consideration. It is shown that the gap in the elementary excitation spectrum is Δ=vFpae−1/ζ,ζ=4(pa/pa)2(e2/a0)(p02/2m). Here νF is the velocity; p0 is the Fermi momentum; pa = 1/2 a (2a is the spacing between domains with electron and hole conductivity); a0 is the spacing between carriers; m = m1m2/(m2+m2)(m1,m2 are the effective masses of the electrons and holes). The system response to a weak magnetic field is calculated; the currents it causes are J1= − J2 = − {[N(T) e2]/( m1+ m2)c2 }(A1− A2)(A1A2 are the values of the vector potential in domains with electron and hole conductivity; J1J2 are the current densities in the appropriate domains; N(T) is the concentration of superconducting electrons). The presence of a stationary Josephson effect is established, i.e., the possibility of superconductivity in the systems under consideration is proved.
Oscillations of the intrinsic magnetoresistance in thin films
Authors: Kolesnichenko Yu. A.
Published: November 2024

The effect of an intrinsic magnetic field on the electrical conductivity of thin semimetallic films whose thickness is comparable with the de Broglie wavelength of the charge carriers is studied. Boundary scattering is assumed to be nearly specular. It is shown that the intrinsic magnetic flow field shifts the size quantization levels of the charge carriers and varies the distance between them. This effect manifests itself in terms of a dependence of the period and amplitude of the size quantization oscillations of the condutivity on current density. The intrinsic magnetic field is taken into account within the framework of perturbation theory.
Phonon spectrum symmetry properties in crystals with CdCl2 structure
Authors: Seidov Yu. M. , Seid-Rzaeva S. M.
Published: November 2024

Group theory methods are used for a full analysis of the branches of the phonon spectrum in crystals with CdCl2-type structure. Normal coordinates are constructed in the longwave limit, with symmetry coordinates at all other points of the Brillouin zone. Conditions for compatibility of irreducible representations in the vicinity of symmetry points are presented. Critical points in the phonon density of states are found, together with selection rules for one and multi-phonon processes in infrared absorption and Raman scattering. Selection rules are obtained for one phonon inelastic scattering of thermal neutrons. Results of the present study agree completely with experimental data on inelastic scattering of neutrons in the FeCl2 crystal. The results obtained are also applicable to other compounds with the CdCl2 structure, namely CoCl2, MnCl2, etc.
Chirality-induced phonon spin selectivity by elastic spin–orbit interaction
Authors: Yang Chenwen , Ren Jie
Published: November 2024

Spin and orbital degrees of freedom are crucial in not only fundamental particles but also classical waves such as optical systems, wherein the spin–orbit interaction (SOI) of light provides new perspectives for manipulating electromagnetic waves. Elastic waves possess similar spin angular momentum (SAM) and orbital angular momentum (OAM). However, the elastic counterpart of SOI remains unexplored, even for ubiquitous elastic waveguides (WG). Here, we demonstrate the existence of elastic SOI in helical WG. We prove that the torsion and curvature of helical WG induces synthetic gauge potentials in describing the elastic vibrations. Through analytical theory and simulations, we unveil the interplay among elastic SAM, intrinsic OAM, and extrinsic OAM, impacted by the elastic SOI. Importantly, results show that elastic SOI can introduce the Chirality-Induced Phonon Spin Selectivity. These findings advance our understanding of angular momentum physics in elastic waves and enable practical strategies for wave manipulation.
Light-regulated chloroplast morphodynamics in a single-celled dinoflagellate
Authors: Schramma Nico , Canales Gloria Casas , Jalaal Maziyar
Published: November 2024

Photosynthetic algae play a significant role in oceanic carbon capture. However, their performance is constantly challenged by fluctuations in environmental light conditions. While phototaxis is a common strategy to cope with such fluctuations, nonmotile species must adopt alternative mechanisms to avoid light-induced damage. Here, we show that the nonmotile, single-celled marine dinoflagellatePyrocystis lunulacontains a chloroplast network that undergoes strong deformation in response to strong light. By exposing cells to various physiologically relevant light conditions and applying temporal illumination sequences, we find that the light-induced network morphodynamics follows dynamic rules similar to temporal low-pass filtering. We develop a mathematical formalism to model the light-regulated behavior, exposing the relevant timescales of the morphodynamic response. Moreover, confocal microscopy reveals that the unusual reticulated morphology exhibits properties similar to auxetic metamaterials, facilitating the rapid and drastic deformation necessary for the light-avoidance motion, confined by the cell wall. This mechanism reduces the effective chloroplast area under high light conditions, minimizing light absorption and preventing photodamage. Our findings demonstrate that the intricate connection between the chloroplasts topologically complex structure and active dynamics enables the dinoflagellate’s dynamic adaptation to changing light environments, thereby supporting essential life-sustaining processes.
Loss of XIST lncRNA unlocks stemness and cellular plasticity in ovarian cancer
Authors: Naciri Ikrame , Liang Minzhi , Yang Ying , Karner Heather , Lin Benjamin , De Lourdes Andrade Ludena Maria , Hanse Eric A. , Lebron Alfredo , Razorenova Olga V. , Nicholas Dequina , Kong Mei , Sun Sha
Published: November 2024

Plasticity, a key hallmark of cancer, enables cells to transition into different states, driving tumor heterogeneity. This cellular plasticity is associated with cancer progression, treatment resistance, and relapse. Cancer stem cells (CSCs) play a central role in this process, yet the molecular factors underlying cancer cell stemness remain poorly understood. In this study, we explored the role of XIST (X-inactive specific transcript) long noncoding RNA in ovarian cancer stemness and plasticity through in silico and in vitro analyses. We found that XIST is significantly down-regulated in ovarian tumors, with low XIST expression linked to a higher stemness index and lower overall survival. Knocking down XIST in ovarian cancer cells enhanced stemness, particularly increasing mesenchymal-like CSCs, and under hypoxic conditions, it promoted epithelial-like CSC markers. Our findings suggest that XIST loss leads to CSC enrichment and cellular plasticity in ovarian cancer, pointing to potential therapeutic targets for patients with low XIST expression.
MCRS1 sensitizes T cell–dependent immunotherapy by augmenting MHC-I expression in solid tumors
Authors: Li Xue , Yi Han , Jin Zheyu , Jiang Kaitao , Xue Kangkang , Wang Jin , Qian Yuping , Xiang Qian , Zhu Sijing , Yan Runhe , Yang Yulong , Sun Shenfei , Li Kai , Zhou Zichu , Yu Wei , Jiang Ning , Ding Chen , Lin Xinhua , Zhong Jiang , Dong Yuchao , Liu Yanfang , Yu Xiaofei
Published: November 2024

Dampened antigen presentation underscores the resistance of pancreatic cancer to T cell–mediated anti-tumor immunity, rendering immunotherapy largely ineffective. By high-throughput CRISPR activation perturbation, we discovered that the transcriptional regulator MCRS1 significantly augmented the sensitivity of mouse pancreatic cancer cells to T cell immunity in vitro and in vivo. Mechanistically, MCRS1 interacted with the transcription factor and genome organizer YY1 to coordinately increase the chromatin accessibility and expression of MHC-I genes. Elevated MCRS1 subverted MHC-I suppression and activated anti-tumor T cells, which sensitized mouse pancreatic cancer to α-PD-1 therapy. Remarkably, high MCRS1 expression was associated with increased T cell infiltration and extended survival of patients with pancreatic cancer and was predictive of favorable responses to α-PD-1 therapy in patients with lung cancer. Together, our study uncovers that MCRS1 sensitizes cancer cells to T cell immunity by transcriptionally subverting MHC-I suppression, which enhances the effectiveness of α-PD-1 therapy in mice and humans, paving the way to further improve immunotherapy against solid tumors.
Determining sources in the bioluminescence tomography problem
Authors: Ding Ming-Hui , Gong Rongfang , Liu Hongyu , Lo Catharine W K
Published: November 2024

In this paper, we revisit the bioluminescence tomography (BLT) problem, where one seeks to reconstruct bioluminescence signals (an internal light source) from external measurements of the Cauchy data. As one kind of optical imaging, the BLT has many merits such as high signal-to-noise ratio, non-destructivity and cost-effectiveness etc and has potential applications such as cancer diagnosis, drug discovery and development as well as gene therapies and so on. In the literature, BLT is extensively studied based on diffusion approximation equation, where the distribution of peak sources is to be reconstructed and no solution uniqueness is guaranteed without adequate a priori information. Motivated by the solution uniqueness issue, several theoretical results are explored. The major contributions in this work that are new to the literature are two-fold: first, we show the theoretical uniqueness of the BLT problem where the light sources are in the shape of C
2 domains or polyhedral- or corona-shaped; second, we support our results with plenty of problem-orientated numerical experiments.
Stable structures and properties of Ru2Al5
Authors: Luo 罗 Jing 晶 , Zhang 张 Meiguang 美光 , Jia 贾 Xiaofei 晓菲 , Wei 魏 Qun 群
Published: November 2024

Novel ordered intermetallic compounds have stimulated much interest. Ru–Al alloys are a prominent class of high-temperature structural materials, but the experimentally reported crystal structure of the intermetallic Ru2Al5 phase remains elusive and debatable. To resolve this controversy, we extensively explored the crystal structures of Ru2Al5 using first-principles calculations combined with crystal structure prediction technique. Among the calculated x-ray diffraction patterns and lattice parameters of five candidate Ru2Al5 structures, those of the orthorhombic Pmmn structure best aligned with recent experimental results. The structural stabilities of the five Ru2Al5 structures were confirmed through formation energy, elastic constants, and phonon spectrum calculations. We also comprehensively analyzed the mechanical and electronic properties of the five candidates. This work can guide the exploration of novel ordered intermetallic compounds in Ru–Al alloys.
Realism-based nonlocality in neutrino oscillations
Authors: Blasone M , De Siena S , Matrella C
Published: November 2024

We resort to the concepts of realism and indefiniteness introduced in Ref. [40], and based on the exploitation of ideal quantum tomography procedures. These concepts are connected to the existence of nonlocal correlations, and moreover allow to introduce a measure of nonlocality. In this paper we apply and test the approach of Ref. [40] in the physically relevant phenomenon of two-flavor neutrino oscillations, both in the plane-wave approximation and in the wave-packet approach, finding meaningful confirmations of the validity of the methodology, which allows to discriminate among distinct characters of different observables, and consequently on their physical relevance.
Polynomial algebra associated to the Cartan subalgebra of G2 in its enveloping algebra
Authors: Campoamor-Stursberg Rutwig
Published: November 2024

The commutant of the Cartan subalgebra of G
2 in its enveloping algebra is determined, showing that it gives rise to a 66-dimensional polynomial algebra of sixth order. It is shown that the commutant of the regular subalgebra A
2 can be obtained by restriction. An illustration how to use these results for Hamiltonian systems with G
2 as spectrum generating algebra is given.
Symmetries of the squeezed Kerr oscillator
Authors: Iachello Francesco
Published: November 2024

The algebraic structure of the squeezed Kerr oscillator sp(2,R)~su(1,1) is described. It is shown that the Kerr oscillator has a novel and hitherto unknown symmetry su(2) which occurs for integer values of the ratio η=Δ/K of detuning Δ to the Kerr coefficient K. The effect of quadratic, cubic and quartic squeezing of the Kerr oscillator is discussed. The results are of importance for the generation and stabilization of states useful for quantum computing.
On classical gravitational corrections to the functional Schrödinger equation
Authors: Reginatto M
Published: November 2024

A full theory of quantum gravity is not yet available, and an approximation in which spacetime remains classical while matter is described by quantum fields is often physically and computationally appropriate. It is therefore of interest to investigate hybrid systems which describe the interaction of classical gravity with quantum matter. Such systems may provide valuable clues relevant to the search of a quantum theory of gravity. Furthermore, one should also consider the possibility that the gravitational field may not be quantum in nature; in that case, it would become necessary to search for a consistent hybrid description.

It is known that the Wheeler-De Witt equation with coupling to quantum fields results in quantum gravitational corrections to the functional Schrödinger equation. A similar result can be obtained for some hybrid models where a classical gravitational field interacts with quantum matter fields. I use the approach of ensembles on configuration space to look at a hybrid model where matter is in the form of a quantized scalar field and determine the corresponding classical gravitational corrections to the functional Schrödinger equation.