JETP Letters最新文献

The crystallization of systems with soft interaction potentials is analyzed for a Yukawa system as an example. The crystallization pathway in the plane of rotational invariants q₄ and q₆ is studied in detail. The recently proposed invariants bcc₁ and bcc₂, calculated using 12 nearest neighbors, are applied for the first time to study the crystallization. It is shown that the combination of the rotational invariant technique and the method of Voronoi polyhedra allows us to identify quite simply all types of solid-like clusters formed during the solidification of the system, including bcc-like clusters, which are hardly identified by conventional methods.

Excitons in MoSe₂ and WSe₂ monolayers encapsulated with hexagonal boron nitride have been studied using optical reflectance spectroscopy. The ground and excited states of A- and B-excitons have been studied at temperatures from liquid helium to room temperature. The lines of excitons A:(1s), B:(1s) and their excited states А:(2s), А:(3s), and В:(2s) are clearly observed in the reflectance spectrum. The observed line shapes of the reflection spectrum of transition metal dichalcogenide monolayers depend on the thickness of the hexagonal boron nitride layers used in the structure and are in good agreement with the numerical simulation using the transfer matrix method. For the first time, the values of the reduced masses of B-excitons have been obtained from experimental data and the performed calculations of the exciton binding energy.

A generalized model of the interaction of a superconducting qubit with the electromagnetic field of a cavity, which is conducted through capacitance (electric dipole interaction) and inductance (magnetic dipole interaction)—the anisotropic Rabi model—is considered. It has been shown that the Hilbert space of the anisotropic model can be split into two subspaces orthogonal in the pseudospin. In this case, the spectra of the Hamiltonians acting in these subspaces have a complex behavior. Analytical and numerical calculations have been performed to clarify the nature of weak chaos in the considered system. The class of universality of the anisotropic Rabi model in the hierarchy of systems with quantum chaos, as well as possible consequences for the theory of quantum measurements, has been discussed.

The effect of Coulomb correlations on the electronic structure of bulk van der Waals material V₂Te₂O is studied by the charge self-consistent density functional theory and dynamical mean-field theory method. Our results show a significant correlation-induced renormalization of the spectral functions in the vicinity of the Fermi energy which is not accompanied by a transfer of the spectral weight to Hubbard bands. The computed quasiparticle effective mass enhancement m*/m for the V (3d) states varies from 1.31 to 3.32 indicating an orbital-dependent nature of correlation effects and suggests an orbital-selective formation of local moments in the V (3d) shell. We demonstrate that taking into account of Coulomb interaction between the V (3d) electrons yields the electronic specific heat coefficient (gamma = 26.94) mJ K^–2 mol^–1 in reasonable agreement with the experiment. We show that the strength of Coulomb correlations is sufficient to trigger a band shift along the Z–Γ–X path of the Brillouin zone leading to a collapse of the electronic Fermi surface pocket centered on the Γ–Z direction predicted by density functional theory.

Tin selenide has record values of the thermoelectric performance, which is largely due to its low lattice thermal conductivity caused by strong lattice anharmonicity. In this work, the effect of temperature and volume on the phonon density of states of the low-temperature SnSe phase with the space group (Pnma) is analyzed using molecular dynamics simulations. Stabilization of the phase with a (Cmcm) crystal structure at high temperatures is demonstrated. An anomalously low lattice thermal conductivity of SnSe is obtained from the numerical solution of the linearized Boltzmann transport equation, which is in agreement with experimental data over a wide temperature range.

The magnetoresistance and the Hall effect in transistor structures fabricated on films of the three-dimensional topological insulator (Bi,Sb)₂(Te,Se)₃ are studied. It is shown that the negative magnetoresistance at low magnetic field is described in terms of quantum corrections to the conductivity. The magnitude of these corrections depends on the gate voltage and increases when approaching the charge neutrality point. The Hall coefficient R_H is nonlinear at low magnetic fields for any gate voltage, and the R_H nonlinearity is the most pronounced at high negative gate voltages. At high fields, the slope of the magnetic field dependence of the Hall coefficient changes its sign at some gate voltage.

The propagation of coupled light beams formed by fast TE modes of a planar waveguide based on a thin left-handed film on a Kerr substrate at a frequency near the frequency of zero group velocity is considered. Conditions for the propagation of three coupled spatial solitons formed by modes with positive and negative group velocities have been determined. The possibility of matched propagation of two bright (dark) solitons and one dark (bright) solitons has been demonstrated.

The magneto-optical Faraday effect is determined by the electric dipole and magnetic dipole transitions in a transparent magnetic material. At the same time, the inverse Faraday effect is still described by an expression that includes only electric dipole transitions. The magnetic dipole contribution to the inverse Faraday effect is considered theoretically, and the dependence of the inverse Faraday effect on the wavelength in the near-infrared range (where the magnetic dipole contribution becomes significant) is obtained by the example of a ferrite–garnet film. It is shown that, although both contributions to the inverse Faraday effect always take place for homogeneous films, only the magnetic-dipole inverse Faraday effect manifests itself for films with a periodic nanostructure upon excitation by a TE waveguide mode, which may be useful for its experimental observation.

It has been shown that the frequency of an ultrashort microwave pulse of a lowest axisymmetric electric mode at the interaction with a counterpropagating relativistic tubular electron beam under the cyclotron resonance conditions can be doubled due to re-emission into a mode having resonance at the second harmonic of the gyrofrequency. The conversion of the 3-cm 1-ns gigawatt microwave pulse in a circular waveguide from the TM₀₁ mode to the TM₀₂ mode with the doubling of the frequency, reduction of the duration to 0.22 ns, and the achievement of the peak power above the initial value has been demonstrated in a numerical experiment. The possibility of forming an intense ultrashort frontal splash of oscillations with the doubled frequency has been shown for longer initial pulses with a subnanosecond front.

Plasmon nanostructures are synthesized for the first time as a result of Cu diffusion into an As₂Se₃ film during the formation of a Cu/As Se film structure by the successive deposition of Cu and As₂Se₃ in vacuum. Using spectroscopic ellipsometry, the spectra of the extinction coefficients and refractive index, as well as the real and imaginary parts of the permittivity of the synthesized structures in the wavelength range of 240–2500 nm, that indicate the presence of localized surface plasmon resonances are obtained. It is shown that the frequency position of plasmon resonances in the wavelength range from 470 to 660 nm can be controlled by changing the thickness of the copper film and annealing.