JETP Letters最新文献

The dynamics of strong plane shock waves (SW) was studied being generated in a hypersonic laser-driven shock tube (LDST) during the acceleration of thin polymer CH films by the ablation pressure of plasma produced by UV pulses of KrF laser (100 J and 100 ns). The LDST has a square cross-section of 7 × 7 mm and a length of 50 mm. At an incident radiation energy density of 70 J/cm² and intensity of 0.7 GW/cm², the SW velocity in air at atmospheric pressure of 2.6 km/s (Mach number M = 8.2) was constant while it propagated in the LDST, and it increased by an additional 30−50% when the laser plasma was confined by a transparent quartz plate. It was shown that the time of quasi-stationary propagation of the SW in the LDST is ~20 μs, being determined by the energy density of the laser pulse imparted to the plasma piston. For comparison, the SW velocity in free space quickly attenuated due to the lateral expansion of the gas, while the SW front acquired the hemispherical shape.

The energies and decay properties of the ground and lower excited levels of the ⁹C nucleus have been calculated with the no-core shell model using the cluster channel orthogonal function method we have developed. Using these data, the cross sections for the ⁸B(p, γ)⁹C radiative capture have been calculated and the astrophysical S factor has been analyzed in a wide range of collision energies. A strong dependence of the S factor at zero energy on positive parity levels in the spectrum of the ⁹C nucleus has been demonstrated.

Silica–aqueous interfaces are the foundation of electrokinetics, microfluidics, and countless physics and biophysics experiments. Yet despite their ubiquity, their molecular structure and electrostatics under flow conditions remain poorly understood. Here we use second-harmonic microscopy combined with Raman spectroscopy in glass microcapillaries, to directly track surface potential dynamics during pH cycling. Acidic and basic transitions from neutral pH conditions drive the interface along distinct kinetic pathways: forward pH jumps elicit instantaneous responses, whereas reverse relaxations are markedly slower, producing path-dependent hysteresis. Extended pH cycling experiments reveal that the silica interface can occupy multiple quasi-stable charge states with surface potential variation from –110 to –25 mV along distinct acid- and base-mediated pathways. Such history-dependent behavior has broad consequences wherever glass substrates are employed, from electrokinetic devices to single-molecule and condensed-matter studies.

We study interaction-induced backscattering mechanism for helical edge states of a two-dimensional topological insulator which is tunnel-coupled to a puddle located near the edge channel. The mechanism does not involve inelastic scattering and is due to the zero-mode fluctuations in a puddle. We discuss in detail a simple model of a puddle, which is a cavity in the bulk of the topological insulator. Such a cavity also has helical edge states with tunneling coupling to helical states encompassing the topological insulator. We analyze effect of the edge current in the puddle. Although averaged value of this current is equal to zero, its zero-mode fluctuations act, in the presence of electron–electron interaction, similar to magnetic flux thus allowing backscattering processes, which involve tunneling through the puddle. Rectification of these fluctuations leads to a finite probability of backscattering. This effect is further enhanced due to dephasing process which is also dominated by zero-mode fluctuations. Remarkably, for temperature exceeding level spacing in the puddle, the rate of backscattering does not depend on temperature in a good agreement with recent experiments.

Experiments on collisions of light nuclei at (sqrt s = 5.36) TeV have recently begun at the LHC. In this regard we make predictions for nuclear modification factor ({{R}_{{AA}}}) in 5.36 TeV C + C, O + O, and Ne + Ne collisions for scenarios with and without quark–gluon plasma formation in (pp) collisions. We find a sizeable difference in ({{R}_{{AA}}}) for these two scenarios, which grows with decreasing atomic number. This says that data on ({{R}_{{AA}}}) for light nuclei could potentially give information on the presence of jet quenching in (pp) collisions.

The topological invariant responsible for the stability of Fermi point/Fermi surface in homogeneous systems is expressed through the one particle Green’s function, which depends on momentum. It is given by an integral over the 3D hypersurface in momentum space surrounding the Fermi surface. Notion of Fermi surface may be extended to the non-homogeneous systems using Wigner–Weyl calculus. The Fermi surface becomes coordinate dependent, it may be defined as the position of the singularity in momentum space of the Wigner transformed Green’s function. Then the topological invariant responsible for the stability of this Fermi surface is given by the same expression as for the homogeneous case, in which the Green’s function is replaced by its Wigner transformation while the ordinary products are replaced by the Moyal products. We illustrate the proposed construction by the examples of the systems, in which the given topological invariant is nontrivial and may be calculated explicitly.

Inelastic effects in the Ising model are analyzed. The Ising model is considered as the Ising field theory with a magnetic field perturbed by the energy density operator (varepsilon ). The inclusion of this operator leads to the emergence of the scattering of the lightest particles in the theory with the formation of two particles (the lightest and the next in mass). The scattering cross section is calculated and its asymptotic forms are determined for high energies and above the threshold.

An all-optical vector magnetometer based on paramagnetic color centers with the spin S = 3/2 in 4H-SiC silicon carbide is presented. The corresponding magnetometry method is based on level anticrossing spectroscopy and does not require the application of microwave power, unlike magnetometry based on optically detected magnetic resonance of nitrogen-vacancy centers in diamond. This eliminates sample heating and simplifies the design of the instrument. It has been shown that the use of “modifying” magnetic fields makes it possible to accelerate the measurement of external magnetic fields with high accuracy. Optical detection of level anticrossing signals in the infrared range provides micron and submicron spatial resolution, which makes the method promising for applications in microelectronics and biomedicine.

The possibility of the formation of a two-frequency light bullet in the second harmonic generation regime in the absence of phase and group velocity matching has been analytically examined. The case where the group velocity dispersion parameter at the frequency of the second harmonic is zero is considered. In this case, this parameter at the fundamental frequency should be negative. It has been shown that the formation of the two-frequency light bullet is insensitive to the sign of the detuning of the group velocities at the fundamental and second harmonic frequencies. At the same time, it is very sensitive to the sign of the detuning between the corresponding refractive indices. Phase and group velocity mismatches lead to upper bounds on the duration and transverse size of the light bullet, as well as to a lower bound on the efficiency of the second-harmonic generation.

The effect of irradiation on the structure, phase transitions, and optical characteristics of a short-pitch cholesteric material forming crystalline liquids (blue phases of liquid crystals) has been studied. The ordering of topological defects (skyrmions) in the irradiated samples leading to a phase transition from the isotropic liquid phase to the ordered cubic structure of skyrmions (blue phase II of liquid crystals) has been found.