Vol 108, No 6 (2018)

A hybrid metasurface realized by a double array of brass wires inserted into two high-permittivity dielectric slabs at both sides was used to perform a magnetic resonance spectroscopy experiment at a 1.5 T clinical magnetic resonance scanner. The metasurface coupled inductively to a transceive birdcage body coil located within the scanner’s bore. The metasurface demonstrated an enhancement of the signal-to-noise ratio of the magnetic resonance spectroscopy experiment in vitro. Up to a signal-to-noise ratio gain of 7.4 for choline and creatine spectral lines was observed in the presence of the metasurface compared to the body coil alone.

³He is an example of the system with non-trivial Cooper paring. A few different superfluid phases are known in this system. Recently the new one, the polar phase, have been observed in ³He confined in nematically ordered aerogel. A number of various topological defects including half-quantum vortices can exist the polar phase. In this work, we present theoretical and numerical studies of linear nuclear magnetic resonance in the polar phase both in the uniform order-parameter texture and in the presence of half-quantum vortices.

Structural transformations of polycrystalline boron have been studied under megabar multiple-shock compression. Shock-wave experiments on the compression and subsequent recovery of polycrystalline samples of β-rhombohedral boron β-B₁₀₆ have been performed. Thermodynamic states of boron under the conditions of the performed experiments have been calculated. According to these calculations, the maximum pressure in the samples is 115 GPa. X-ray diffraction analysis of the stored boron samples has been performed. It has been shown that the dynamic compression of polycrystalline β-B₁₀₆ to 115 GPa results in its partial amorphization and transformation to the tetragonal modification of boron T-B₁₉₂.

The spin polarization features of an electron system and the relaxation of nonequilibrium spin excitations near an even-denominator fractional state of 3/2 in a two-dimensional electron system based on the GaAs/AlGaAs heterostructure are experimentally investigated. It is shown that the 3/2 state is a singular point in the filling factor dependence of the spin ordering of the two-dimensional electron system, at which the spin subsystem is rearranged. A giant slowing down of the relaxation of spin excitations to the ground state is revealed in a certain range of filling factors near filling factor 3/2.

The width of the \(\tau\rightarrow\bar{K}^{*0}(892)\pi^{-}\nu_\tau\) decay is calculated within the Nambu–Jona-Lasinio model taking into account four channels of the formation of the \(\tau\rightarrow\bar{K}^{*0}(892)\pi^{-}\) pair—the contact interaction and three channels with intermediate axial-vector, vector, and pseudoscalar mesons. Leading contributions arise from the contact interaction and axial-vector channel with an intermediate ground-state K₁(1270) meson. Our theoretical estimate adequately reproduces the measured \(\tau\rightarrow\bar{K}^{*0}(892)\pi^{-}\nu_\tau\) decay width.

The nature of two dusty plasma clouds appearing because of the impact of a meteoroid on the surface of the Moon has been discussed. It has been shown that one of the clouds is formed by particles (or fragments) of regolith ejected into free space by a shock wave induced by the meteoroid impact on the surface of the Moon and the second cloud is formed by solidified melt droplets. The main characteristics of these clouds, including the cloud expansion rates, the characteristic sizes of particles in both clouds, and the concentrations and charges of particles, have been calculated. The calculated cloud expansion rates are in qualitative agreement with the observational data.

The possibility of acoustic detection of submicron displacement of a metal surface during ablation induced by a nanosecond (∼550 ns) train of ∼70 short (∼60 ps) laser pulses has been demonstrated experimentally for the first time. The detection is based on the comparison of time structures of modulation of the laser intensity and recoil pressure in an irradiated target observed by a piezoelectric sensor. The displacement at low intensities of irradiation is due to thermal expansion. With an increase in the intensity, the displacement changes sign because of the development of ablation processes in the irradiated region. The proposed method makes it possible to obtain new information on the behavior of a material, in particular, under the conditions of extreme phase nonequilibrium under intense laser irradiation.

The spectral characteristics of the hole photocurrent in plasmon photodetectors based on Ge/Si heterostructures with Ge quantum dots combined with regular arrays of subwavelength apertures of various shapes in a gold film on the semiconductor surface are investigated. Dispersion relations characterizing the propagation of surface plasmon waves along the metal–semiconductor interface are determined from the dependences of the photocurrent on the angle of incidence of light. It is established that the plasmonic enhancement of the photocurrent in rectangular aperture array is suppressed as compared to that in circular and square aperture arrays. It is found that, in hybrid structures with rectangular apertures, there exists a range of wave vectors where the energy of surface plasmons is independent of the wave vector of incident radiation. The results are explained by the excitation of dipole modes localized at rectangular apertures with a large aspect ratio by light waves.

It has been shown that space–time inversion symmetry breaking at the normal incidence of a quasiplane wave on an asymmetric multilayer structure in the Voigt geometry can result in the formation of the angular Goos–Hänchen effect at reflection and transmission, as well as the spatial Goos–Hänchen effect at transmission. The effects are characterized by nonreciprocity not only with respect to the inversion of direction of static magnetic field but also with respect to the permutation of nongyrotropic layers surrounding a gyrotropic layer.

The first experimental results on the dynamics of a plasma cloud produced by a miniature coaxial gun in a magnetized background plasma have been reported. The record dimension of the plasma in the Krot device, which is more than 1 m across a magnetic field, has allowed the first implementation of the regime of “unbounded” background plasma, which is optimal for the simulation of astro- and geophysical phenomena. In the sub-Alfvénic regime of cloud expansion, a set of characteristic effects has been demonstrated, including the formation of a diamagnetic cavity, deceleration of ions of the cloud by the background plasma, and development of high-frequency instability at the edge of the cloud.