Journal of Experimental and Theoretical Physics最新文献

The spectra of the optically detected magnetic resonance for single NV^– centers have been experimentally studied in two solid-state samples in the range of hyperfine interactions between the electron spin and the nitrogen nucleus spin in the same NV^– center. This study has been aimed at reaching a maximal microwave frequency resolution in the experimental setup used. For measurements, two low-nitrogen (no higher than 50 ppb) diamond single-crystal samples have been grown. Measured time (T_{2}^{*}) of the spin decoherence in NV^– centers was about 2 μs in one sample and 20 μs in the other. For both samples, the spectrum of the optically detected magnetic resonance for the hyperfine splitting of a single NV^– center and ¹⁴N atom has been taken and investigated. The resolution in these samples has been estimated at a level of 3.5 and 0.18 MHz, respectively. It has been noted that the resolution of the spectrum improves with increasing time (T_{2}^{*}) of the spin decoherence of the single NV^– center.

Two devices intended for copper cylindrical liner gasdynamic acceleration to velocities of 5–7 km/s using the chemicals explosion energy have been investigated. It has been demonstrated that the acceleration of quasi-isentropically and isentropically loaded liners under the conditions of high-level dynamics, symmetry of deposition, and suppression of shock-induced dusting is feasible.

We have performed the Monte Carlo simulation of the processes of secondary ionization of water induced by cascade decays of inner-shell vacancies in an iron atom placed in water. We have obtained the spectra of electrons and photons emitted during the decay of vacancies in the K and L shells of the iron atom. The dependences of the number of secondary ionization events and the energy absorbed as a result of these processes on the radius of the sphere in which such processes occur have been calculated. The decay of a single 1s vacancy in an iron atom generates on the average 232 events of secondary ionization induced by an electron impact, in which the energy of 3274 eV is absorbed, as well as 18 secondary photoionization events, in which the energy of 256 eV is absorbed. The dependences of the dose absorbed in water on the distance from the iron atom have been calculated.

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.

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.

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.