Journal of Experimental and Theoretical Physics最新文献

We review and extend some recent work on testing AdS/CFT correspondence between U(N)_k × U(N)_–k Chern-Simons-matter 3d gauge theory and M-theory in AdS₄ × S⁷/Z_k background. We demonstrate that 1-loop term in the quantum M2 brane partition function expanded near a classical solution correctly matches localization predictions on the gauge theory side in the case of BPS Wilson loop expectation value and instanton corrections to free energy.

The application of neutron powder diffraction to search for a new internucleon Yukawa-like interaction is considered. The essence of the method is in the investigation of dependency of the neutron scattering amplitude on the momentum transfer. The possible contributions to the scattering amplitude and to the integrated intensity of diffraction maxima were analyzed. The neutron diffraction experiment with silicon powder at D20 diffractometer of the ILL reactor (Grenoble, France) was performed. From the data obtained constraints on the coupling constant of the considered interaction were made. It is shown that in the interaction radius range of λ = 10^–13–10^—11 m they improve the values already existing in the literature. The result obtained is limited by imperfections of the experimental setup. Eliminating the instrumental contribution may allow increasing the sensitivity of the method by at least an order of magnitude.

A domain wall (DW) which moves parallel to a magnetically compensated interface between an antiferromagnetic insulator (AFMI) and a two-dimensional (2D) metal can pump spin polarization into the metal. It is assumed that localized spins of a collinear AFMI interact with itinerant electrons through their exchange interaction on the interface. We employed the Keldysh formalism of Green’s functions for electrons which experience potential and spin-orbit scattering on random impurities. This formalism allows a unified analysis of spin pumping, spin diffusion and spin relaxation effects on a 2D electron gas. It is shown that the pumping of a nonstaggered magnetization into the metal film takes place in the second order with respect to the interface exchange interaction. At sufficiently weak spin relaxation this pumping effect can be much stronger than the first-order effect of the Pauli magnetism which is produced by the small nonstaggered exchange field of the DW. It is shown that the pumped polarization is sensitive to the geometry of the electron’s Fermi surface and increases when the wave vector of the staggered magnetization approaches the nesting vector of the Fermi surface. In a disordered diffusive electron gas the induced spin polarization follows the motion of the domain wall. It is distributed asymmetrically around the DW over a distance which can be much larger than the DW width.

The interaction of a titanium carbide nanoparticle with aluminum (100), (110), and (111) substrates is investigated within the density functional theory. The nanoparticle–substrate interaction energies are determined; the electron density distribution and the electron localization function between aluminum, titanium, and carbon atoms are analyzed. It has been established that the atoms in the upper layers of the aluminum (100) and (110) substrates are significantly displaced relative to their initial positions as a result of the interaction with the nanoparticle, whereas a minor displacement of atoms is typical for the (111) substrate. The interaction between aluminum and carbon atoms at the Al–TiC interface is due to the formation of covalent Al–C chemical bonds. The aluminum atoms forming carbide bonds do not form chemical bonds with titanium atoms. The aluminum atoms that are adjacent to the titanium atoms and are not involved in the formation of carbide bonds form metallic Al–Ti bonds.

We present comparative theoretical investigation of thermoelectric power and Hall effect in the Hubbard model for correlated metal and Mott insulator (considered as prototype cuprate superconductor) for different concentrations of current carriers. Analysis is performed within standard DMFT approximation. For Mott insulator we consider the typical case of partial filling of the lower Hubbard band (hole doping). We calculate the dependence of thermopower on doping level and determine the critical concentration of carriers corresponding to sign change of thermopower. An anomalous dependence of thermopower on temperature is obtained significantly different from linear temperature dependence typical for the usual metals. The role of disorder scattering is analyzed on qualitative level. The comparison with similar studies of the Hall effect shows, that breaking of electron-hole symmetry leads to the appearance of the relatively large interval of band-fillings (close to the half-filling) where thermopower and Hall effects have different signs. We propose a certain scheme allowing to determine the number of carriers from ARPES data and perform semi-quantitative estimate of both thermopower and Hall coefficient using the usual DFT calculations of electronic spectrum.

Under conditions of total internal reflection (TIR) of a plane bulk electromagnetic wave incident from outside on the surface of an optically transparent layered structure, the case where the numerator and denominator of the input surface wave impedance turn simultaneously to zero may correspond to the formation of a “dark” state. This is related to the occurrence of a point of degeneracy of the spectra of leaking exceptional surface waves (ESWs) of the first and second kind against the background of the continuous spectrum of radiative modes. For these waves, the instantaneous energy flux through the interface with a semibounded optical denser medium in an open radiative channel is zero at any instant. When approaching the point of dark state occurrence, the local maxima of the effects of first-order nonspecular reflection, accompanying resonant excitation of leaky ESWs, unlimitedly increase.

The article by R. M. Feshchenko (J. Exp. Theor. Phys. 136, 406 (2023)) is devoted to an important issue concerning general properties of electromagnetic field pulses and contains, in particular, critical remarks on our publications (R. M. Arkhipov et al. Quant. Electronics 50, 801 (2020); R. Arkhipov et al., Laser Field Lett. 19, 043001 (2022), and M. V. Arkhipov et al., JETP Lett. 115, 1 (2022)). We reply to these critical remarks and indicate a number of inaccuracies in the aforementioned article.

The structure of nuclear matter at short internucleon distances is one of the poorly studied aspects of nuclear physics. At distances of the order of the nucleon radius, nuclear matter is represented by the pairs of correlated nucleons with relative momenta exceeding the Fermi momenta that emerge for a short time. Such structures, whose local density is comparable to the density of neutron stars, arise from fluctuations in the average nuclear density. One of the important characteristics of nucleon–nucleon correlations is their universality implying the independence of their properties from the nuclear mass number. Therefore, the peculiarities of these objects of nuclear structure reflect the properties of nuclear matter rather than specific nuclei. Information about the short-distance physics is extracted from the analysis of processes with high energy–momentum transfers. Until now, the property of universality has been observed in electron–nucleus collisions only for the breakup of nucleon pairs. In this paper we analyze the data on the cumulative production of pions by protons on a set of nuclear targets and for the first time have established the existence of universality of two-nucleon correlations in the production of π⁺ and π^– mesons. We have obtained evidence for the involvement of three-nucleon correlations in the production of pions beyond the kinematics of their production in interactions with two-nucleon objects.

The gauge SU(2)_L × U(1) model with the extension of the lepton sector by three right-handed Majorana sterile neutrinos is considered. The complete mass matrix of 6 × 6 active and sterile neutrinos is diagonalized. The cosmological bounds following from the lifetime of sterile neutrinos and the fraction of energy carried by sterile neutrino dark matter are obtained. The deviations from the “fine-tuned” mixing scenario sensitive to the mass of the lightest standard (active) neutrino are considered, and the regions of the model parameter space corresponding to these deviations are distinguished.

Exact analytic expressions are derived for the spectrum and wavefunctions of electrons in a monolayer of transition metal dichalcogenides in crossed electric and magnetic fields. The electric field dependence of interband transition intensity is calculated. The valley selectivity of interband absorption considerably depends on the electric field and can reverse its sign multiply upon an increase in this field.