Том 107, № 5 (2018)

The time reversal symmetric polar phase of the spin-triplet superfluid ³He has two types of Dirac nodal lines. In addition to the Dirac loop in the spectrum of the fermionic Bogoliubov quasiparticles in the momentum space (p_x, p_y, p_z ), the spectrum of bosons (magnons) has Dirac loop in the 3D space of parameters—the components of magnetic field (H_x,H_y,H_z ). The bosonic Dirac system lives on the border between the type-I and type-II.

The spin-valve effect in superconductor hybrid structures based on magnetic materials with a noncollinear magnetic ordering is described theoretically. It is shown that the following effect is possible in such structures: when the sample is magnetized, the critical temperature of the superconducting transition increases. The origin is the suppression of long-range triplet superconducting correlations. Such structures can be used as newtype memory elements for superconducting spintronics.

The behavior of the specific heat of MnS₂ at high pressures has been studied. A significant increase in the transition temperature T_N to an antiferromagnetic state with the pressure from 48.2 K at atmospheric pressure to 76 K at a pressure of 5.3 GPa has been revealed. The initial pressure derivative is dT_N/dP = 4.83 K/GPa. It has been found that the parameter α = d(logT_N)/d(logV ) = −6.6 ± 0.1 is significantly different from the value α = −10/3 ≈ −3.3 (Bloch relation), which is typical of numerous antiferromagnetic insulators—transition- metal oxides and fluorides. The volume jump at the magnetic transition point has been estimated. The necessity of direct dilatometric measurements of the volume has been justified.

The mass and the wave function of doubly charmed Ξ_cc⁺⁺ (ccu) baryon are evaluated using Green Function Monte Carlo method to solve the three-body problem with Cornell potential. The mass of Ξ_cc⁺⁺ with spin 1/2 is in a good agreement with the LHCb value. Simulation of the wave function by random walks resulted in a configuration of the quark–diquark type. The radius of Ξ_cc⁺⁺ is much larger than the size needed for a large isospin splitting. The prediction for the Ω_cc mass is presented.

The elastic scattering of two X-ray photons by a multicharged atomic ion has been studied theoretically. A pronounced resonance structure and strong angular anisotropy of differential scattering cross section have been predicted in the energy range of a scattered photon from ℏω–I_1s to ℏω+I_1s (where is the energy of the incident photon and is the ionization energy threshold of the shell of the ion). The absolute value of the observed cross section has been quantitatively estimated.

Pulses with a spectral width of 450 nm at a wavelength of 2.2 μm are generated in a parametric amplifier based on a type-I BBO crystal pumped by the second harmonic (620 nm) of a Cr:forsterite laser. Such a broadband radiation is obtained in a specific regime of the group velocity matching near the vertical region of the tuning curve. The generated pulses can be compressed to a duration of about 2.5 optical cycles (34 fs) in a medium with positive group-velocity dispersion.

A method for formation of bulk plasmonic structures based on porous quartz with silver nanoparticles in pores has been proposed and implemented. The spectroscopy of their optical and nonlinear optical properties has been performed by methods of second harmonic generation and two-photon absorption. A significant increase in the nonlinear absorption coefficient has been detected in the plasmon resonance region. The enhancement of the second optical harmonic has been observed with the shift by tens of nanometers from the plasmon resonance position toward the long-wavelength region.

The internal structure of dissipative topological solitons has been revealed by example of three-dimensional dissipative optical solitons with one open and one closed dislocation lines of a wavefront. This structure is manifested in the existence of critical points, lines, and surfaces in the field of electromagnetic energy fluxes (Poynting vector). The conservation of the topological characteristics of such solitons, which can be formed in a homogeneous laser medium with saturated amplification and absorption or in lasers with quite large longitudinal and transverse dimensions, provides additional capabilities for information applications.