Application of the ultrasonic velocity profile method to the mapping of liquid metal flows under the influence of a non-uniform magnetic field

An ultrasonic velocity profile (UVP) method has been successfully applied to the investigation of a liquid metal channel flow under the influence of an inhomogeneous magnetic field. Using velocity profiles obtained by the ultrasonic velocimeter and their numerical post processing, two-dimensional time-averaged flow maps were efficiently produced. A single transducer immersed directly into the working fluid was used in order to simplify alignment of measurement lines and avoid the undesirable refraction of the acoustic beam on the walls. An M-shaped flow and wake behind a magnetic obstacle were reconstructed as the patterns of shear and large-scale vortical flows.     

Light scattering by a finite obstacle and fano resonances

The conditions for observing Fano resonances at elastic light scattering by a single finite-size obstacle are discussed. General arguments are illustrated by consideration of the scattering by a small (relative to the incident light wavelength) spherical obstacle based upon the exact Mie solution of the diffraction problem. The most attention is paid to recently discovered anomalous scattering. An exactly solvable one-dimentional discrete model with nonlocal coupling for simulating diffraction in wave scattering in systems with reduced spatial dimensionality is also introduced and analyzed. Deep connections between the resonances in the continuous and discrete systems are revealed.     

Generation and dynamics of vortex lattices in coherent exciton-polariton fields

Vortex dynamics in coherent ensembles of exciton polaritons (condensates) is studied in the framework of the polarization-dependent Gross-Pitaevskii equation. Vortex lattices can be resonantly excited in the polariton field by the interference of three or more optical pumps. Vortex-antivortex pairs can also appear in polariton condensates due to scattering with disorder. The nonlinear vortex dynamics is characterized by interactions of vortex cores and vortex-antivortex recombination.     

Defect-free surface states in modulated photonic lattices

We predict that interfaces of periodically curved waveguide arrays can support a novel type of surface states which exist in a certain region of modulation parameters associated with the band flattening. Such linear surface states appear in truncated but otherwise perfect (defect-free) lattices as a direct consequence of the periodic modulation of the lattice potential. We show that the existence of these modes in different band gaps can be flexibly controlled by selecting the modulation profile, with no restrictions on Bloch-wave symmetries characteristic of Shockley states.     

Spatiotemporal toroidal waves from the transverse second-harmonic generation

We study the second-harmonic generation via transversely matched interaction of two counterpropagating ultrashort pulses in chi(2) photonic structures. We show that the emitted second-harmonic wave attains the form of spatially expanding toroid with the initial thickness given by the cross correlation of the pulses. We demonstrate the formation of such toroidal waves in crystals with random ferroelectric domains as well as in annularly poled nonlinear photonic structures.     

Spiraling multivortex solitons in nonlocal nonlinear media

We demonstrate the existence of a broad class of higher-order rotating spatial solitons in nonlocal nonlinear media. We employ the generalized Hermite-Laguerre-Gaussian ansatz for constructing multivortex soliton solutions and study numerically their dynamics and stability. We discuss in detail the tripole soliton carrying two spiraling phase dislocations, or self-trapped optical vortices.     

On the viscous and inviscid stability of magnetohydrodynamic shock waves

We study the viscous and inviscid stability of shock waves in barotropic and full magnetohydrodynamics. We show that there are magnetohydrodynamic shock waves that are one-dimensionally stable as viscous shock profiles while they are multidimensionally strongly unstable as planar shock discontinuities.     

Effect of electric fields on the dynamics of silicon microhardness changes induced by low-intensity β irradiation

Decelerating effect of electric fields on silicon microhardness changes induced by low-intensity (I = 10.4 × 10⁴ cm^?2 s^?1) β irradiation has been revealed. The threshold character of the electric field effect is found (the effect is absent at electric fields E < 350 V cm^?1).     

The quadrupole mechanism of hole spin relaxation

For spin-3/2 holes the anisotropic part of the instantaneous Luttinger Hamiltonian can be represented as an effective quadrupole coupling. We investigate the hole spin relaxation process induced by nonadiabatic fluctuations of this interaction. The obtained analytical solution of the stochastic Liouville equation describes the polarization decay of spin-3/2 holes in all regimes of momentum scattering: from collision-dominated to ballistic. Our results create the basis for quantitative interpretation of recent experiments and elucidate the striking difference between the hole spin relaxation process in bulk crystals and 2D semiconductor nanostructures.