卷 107, 编号 1 (2018)

The sensitivity of the method of neutron scattering to novel neutron–nucleon interactions is analyzed. Upper limits on the coupling constant of such interactions are imposed using the available data on neutron powder diffraction on polycrystalline silicon. For the forces acting at ranges of λ < 10^–11 m, these upper limits are already competitive with the best existing constraints on their coupling constant. A dedicated experiment can help improve the sensitivity to this coupling constant by nearly two orders of magnitude.

An experimental method has been proposed to study the dispersion properties of optical surface and waveguide modes in planar structures. An experimental setup involves a microscope with a high numerical aperture objective and a hemispherical solid immersion lens made of zinc selenide in contact with the sample surface. The reflection from the sample is detected in the back focal plane of the system. Such a configuration makes it possible to study strongly localized states with an effective refractive index up to 2.25 in the visible and near infrared spectral ranges. For a thin silicon layer deposited on a glass substrate, the possibility of visualization of isofrequency contrours with polarization resolution and the reconstruction of dispersion of waveguide modes depending on the direction of their propagation has been demonstrated.

A method has been developed for the calculation of tensors of the electrical conductivity, Seebeck coefficient, and thermal conductivity of a nonideal plasma in a magnetic field within a unified approach where the kinetic coefficients are calculated together with the equation of state of the nonideal plasma within a quasichemical model. The calculations have shown that the Seebeck coefficient in xenon reaches 3 mV/K, which is slightly smaller than that in hydrogen or deuterium, and the figure of merit appears to be insignificantly higher in xenon. Consequently, the transition from hydrogen (deuterium) to xenon does not result in the expected noticeable improvement of thermoelectric properties. This is due to lower values of the Seebeck coefficient and electrical conductivity, as well as to a fast increase in the thermal conductivity of neutral xenon with an increase in its density. It has been shown for the first time that there is a density range where all components of the Seebeck tensor in xenon change their sign because of the Ramsauer minimum in the cross section for scattering of electrons on neutral atoms in the region of comparable values of cyclotron and transport frequencies of electrons.

The spin-wave dynamics in the system of lateral magnetic microstructures have been studied experimentally and numerically. Regimes of the propagation of coupled spin waves have been investigated by Brillouin spectroscopy measurement and numerical experiment. A phenomenological model has been proposed to describe the properties of spin waves in a lateral structure. It has been shown that the length of the coupling between spin waves can be governed by varying the power of the signal. The results can be used to fabricate magnetic waveguides of spin-wave demultiplexers, power splitters, and microwave couplers based on the lateral system.

The trapped magnetic flux in the finely ground pyrolytic graphite sample annealed at 670 K in air has been observed. Flux trapping occurs on cooling of the sample from room temperature to 10 K in a magnetic field of 1 T. The magnitude and sign of the induced trapped moment remain unchanged when the applied magnetic field is varied within ±1 T at T K. The trapped magnetic flux is manifested in the displacement of the magnetization curve relative to that of the sample cooled in zero field. Displacement magnitude gradually decreases with the temperature increase up to 350 K, not reaching zero. The set of experimental observations probably reflects the presence in the sample of a granular high-temperature superconducting phase.

An analytical approach that makes it possible to reconstruct the current–phase relation (CPR) in Josephson structures included in one of the arms of a two-junction superconducting quantum interference device (SQUID), where the second junction has a significantly higher critical current and a known (sinusoidal) CPR, has been developed. The developed methods of analytical and numerical studies of current–flow transformations in two-junction SQUIDs make it possible to reconstruct the CPR of a junction with a low critical current taking into account both the existence of the self-inductance of the interferometer contour and a possible asymmetry in the supply current system. The efficiency of this approach has been confirmed by the experimental study of niobium–aluminum/aluminum oxide–niobium test structures with the known CPR.

The temperature dependence of the switching frequency of a microwave-induced spontaneous electric field forming a domain structure and the conductance of a doping layer that provides electrons to the two-dimensional electron system have been measured on samples fabricated from the same GaAs/AlGaAs heterostructure. Both quantities have been found to obey the thermally activated dependence (Arrhenius law) with close activation energies. This result indicates a relation between the quantities and confirms a hypothesis that the observed dynamics of the domain structure originates from the dynamical screening of the spontaneous electric field of domains by charges in the doping layer.

The experimentally observed incomplete fluorination of graphene (CF_x, x ≤ 0.2−0.3) on a smooth substrate has been explained. It has been shown that fluorine atoms are covalently attached primarily to scanty folds or to defects of graphene on one of its free sides.