Neutrino-Oscillation Searches in the Short-Baseline Gallium Experiment BEST-2 with a 65Zn Source

The possibility of employing a ⁶⁵Zn source in the gallium experiment BEST-2 with the aim of constraining the region of allowed oscillation parameters is examined. The source activity required for the BEST-2 experiment is calculated, and the size of the source and its effect on the results of oscillation measurements are discussed along with the possibilities for producing such a source. Various schemes for implementing respective measurements are considered.

     

Anomalous quasiparticle renormalization in Na0.73CoO2: role of interorbital interactions and magnetic correlations

We report an angular resolved photoemission study of NaxCoO2 with x approximately 0.73 where it is found that the renormalization of the quasiparticle (QP) dispersion changes dramatically upon a rotation from GammaM to GammaK. The comparison of the experimental data to the calculated band structure reveals that the quasiparticle renormalization is most pronounced along the GammaK direction, while it is significantly weaker along the GammaM direction. We discuss the observed anisotropy in terms of multiorbital effects and point out the relevance of magnetic correlations for the band structure of NaxCoO2 with x approximately 0.75.     

Effect of Zn and Ni impurities on the quasiparticle renormalization of superconducting Bi-2212

The Cu substitution by Zn and Ni impurities and its influence on the mass renormalization effects in angle-resolved photoelectron spectra (ARPES) of Bi2Sr2CaCu2O8-delta is addressed. We show that the nonmagnetic Zn atoms have a much stronger effect in both the nodal and antinodal parts of the Brillouin zone than magnetic Ni. The observed changes are consistent with the behavior of the spin resonance mode as seen by inelastic neutron scattering in YBCO. This strongly suggests that the "peak-dip-hump" and the kink in ARPES on the one side and neutron resonance on the other are closely related features.     

Energy spectrum and optical absorption in p-CdGeAs2

In the Kein four-band model, taking account of interaction with excited bands, the energy spectrum and effective masses of electrons and holes in CdGeAs₂ are calculated. The polarizational dependence of the optical absorption spectrum is investigated for transitions between bands of light and heavy holes. The results are compared with experimental data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 68–72, January, 1982.     

Thermal Degradation of Polyvinylpyrrolidone on the Surface of Pyrogenic Silica

Thermal degradation of polyvinylpyrrolidone was studied by thermogravimetry, IR spectroscopy, and thermal-desorption mass spectrometry.     

Exponential corrections to low-temperature expansion of 2D non-abelian models

The thermodynamic limit of certain exponential corrections to the weak coupling expansion of two-dimensional models is investigated. The expectation values of operators contributing to the first-order coefficient of the low-temperature expansion of the free energy are calculated for the order O(e^−β). They are proven to diverge logarithmically with the volume for non-abelian models.     

Effect of Miniband Dispersion on Inelastic Scattering of Superlattice Electrons by Acoustic Phonons

Within the framework of the Boltzmann equation, formulas for calculating the effective relaxation time and mobility of superlattice electrons are derived with allowance for inelastic scattering on acoustic phonons and dispersion of the miniband energy spectrum depending on the longitudinal wave vector. The dependences of longitudinal and transverse mobilities of the nondegenerate electronic gas of the GaAs/Al_0.36Ga_0.64As superlattice with the quantum well 5 nm wide on the potential barrier width and temperature are analyzed numerically. It is demonstrated that inelasticity of scattering and miniband dispersion significantly increase the electron mobility, and its temperature dependence becomes more pronounced at low temperatures.     

Memory element based on Si/CaF<Subscript>2</Subscript> periodic nanostructures

A memory element based on a Si/CaF₂ periodic nanostructure is proposed. In this element, information is recorded through charge capture by trap states in a CaF₂ dielectric. The high and low signal levels correspond to the current in the maximum and minimum of the negative differential resistance region, which forms as a result of the resonant tunnel distribution of charge carriers over trap levels in the dielectric. The speed of such logical elements depends on the rate of activation carrier trapping and the rate of tunnel carrier transfer from one state to another. It is shown that both Si/CaF₂-based logical elements and memory elements proposed operate at temperatures from 77 to 300 K, have a switching time of 10⁻¹²–10⁻¹⁰ s, and are compatible with silicon IC technology.     

Explosive transition in amorphous microwire

An amorphous microwire in a glass shell offers a quick thermal response and can be rapidly heated to the crystallization point. When heated by a current pulse with a small amplitude and duration, the wire passes from the amorphous to microcrystalline state. The crystallization of the amorphous state may represent a slow or explosive process depending on the parameters of the pulse. In the latter case, the emission of electromagnetic waves (flash of light) and a sharp rise in the resistance are observed. The rate of propagation of the crystallization front in our experiments has been found to be about 1 m/s.     

Recrystallization of pure and strontium-doped KCl crystals

The kinetics of microstructure transformations are studied during annealing of deformed single crystals of KCl and KCl:0.05wt %Sr²⁺ at temperatures of (0.35–0.55)T _m (where T _m is the melting temperature) and during storage at room temperature. The effect of deformation rates ranging from 0.01 mm/min to 0.1 mm/min at a deformation temperature T _d=0.5T _m on the crystal structure and on the recrystallization kinetics is noted. It is found experimentally that the incubation period for static recrystallization in single-crystal KCl:0.05wt%Sr²⁺ is shortened and recrystallization takes place at room temperature after deformation in this temperature range. Here, during the new recrystallization grains have a twinned orientation with respect to the initial single crystal during the first stage and to the subgrains of the deformed crystal. As the annealing temperature is raised, the stage in which twins grow in KCl:0.05wt%Sr²⁺ crystals is shortened and it is displaced by recrystallization through migration of high-angle grain boundaries of the common type. Deformation conditions which ensure prolonged (at least three months) stability of the post-deformation hardening of single crystals are found experimentally for Sr²⁺-doped deformed single crystals. Fiz. Tverd. Tela (St. Petersburg) 41, 259–264 (February 1999)