arXiv subjects

M. A. Liberman

Publications and source records attributed to M. A. Liberman.

15 recordsLinked to original sources

arXiv2020

Two-dimensional electron-hole system under the influence of the Chern-Simons gauge field created by the quantum point vortices

In the present work the Chern-Simons(C-S) gauge field theory developed by Jackiw and Pi [1] and widely used to explain the fractional quantum Hall effects, was applied to describe the two-dimensional (2D) electron-hole (e-h) system in a strong perpendicular magnetic field under the influence of the quantum point vortices creating the Chern-Simons(C-S) gauge field. The composite particles formed by electrons and by holes with equal integer positive numbers of the attached quantum point vortices are described by the dressed field operators, which obey to the Fermi or to the Bose statistics depending on the even or odd numbers . It is shown that the phase operators as well as the vector and the scalar potentials of the C-S gauge field depend on the difference of the electron and of the hole density operators. They vanish in the mean field approximation, when the average values of the electron and of the whole densities coincide. Nevertheless, even in this case, the quantum fluctuations of the C-S gauge field lead to new physics of the 2D e-h system.

cond-mat.quant-gas↗

arXiv2019

Metastable bound states of the quasi-bimagnetoexcitons in the lowest Landau levels approximation

Four different spin structures of two electrons and of two holes situated on the lowest Landau levels (LLLs) are taken into account to investigate possible bound states of the two-dimensional magnetic biexciton formed of two magnetoexcitons with opposite wave vectors and antiparallel dipole moments. The singlet and triplet states of the spins of two electrons and of two holes separately, as well as of two para- and two ortho-magnetoexcitons are considered. The general expressions describing the binding energy of the bound states and the normalization conditions characterized by the effective spin parameter for the corresponding wave functions are derived. The most favorable of the four considered spin configurations happened to be the triplet-triplet spin structure of two electrons and of two holes. In its frame a metastable bound state with activation barrier comparable with two ionization potentials of the magnetoexciton is revealed .

cond-mat.mes-hall↗

arXiv2018

Metastable bound states of the of the interacting 2D magnetoexcitons

The possible formation of two-dimensional (2D) magnetic bi-excitons composed of two 2D magnetoexcitons with electrons and holes on the lowest Landau levels (LLLs), with opposite center of- mass wave vectors k and and with antiparallel electric dipole moments perpendicular to the corresponding wave vectors was investigated. Two spinor structures of two electrons and of two holes were considered. In the singlet-singlet state the spins of two electrons as well as the effective spins of two holes create the combinations with the total spin S=0 and its projection on the magnetic field The triplet-triplet state corresponds to S=1. Two orbital Gaussian variational wave functions depending on | k | and describing the relative motion of two magnetoexcitons inside the molecule were used. It is shown that in the LLLs approximation the stable bound states of bimagnetoexcitons do not exist. A metastable bound state for the triplet-triplet spin configuration a metastable bound state with the orbital wave function, having the maximum on the in-plane ring was revealed. The metastable bound state has an energy activation barrier comparable with the magnetoexciton ionization potential and gives rise to the new luminescence band due to the metastable bi-exciton-para exciton conversion with the frequencies higher than those of the para magnetoexciton luminescence line.

cond-mat.mes-hall↗

arXiv2018

Metastable bound states of the two-dimensional bi-magnetoexcitons in the lowest Landau levels approximation

The possible existence of the bound states of the interacting two-dimensional (2D) magnetoexcitons in the lowest Landau levels (LLLs) approximation was investigated using the Landau gauge description. The magnetoexcitons taking part in the formation of the bound state with resultant wave vector k= 0 have opposite in-plane wave vectors and look as two electric dipoles with the arms oriented in-plane perpendicularly to the corresponding wave vectors. The bound state of two antiparallel dipoles moving with equal probability in any direction of the plane with equal but antiparallel wave vectors is characterized by the variational wave function of the relative motion depending on the modulus | k |. The spins of two electrons and the effective spins of two holes forming the bound states were combined separately in the symmetric or in the antisymmetric forms for electrons and holes. In the case of the variational wave function the maximum density of the magnetoexcitons in the momentum space representation is concentrated on the in-plane ring. The stable bound states of the bimagnetoexciton molecule do not exist for both spin orientations. Instead of them, a deep metastable bound state with the activation barrier comparable with the ionization potential of the magnetoexciton with k =0 was revealed.

cond-mat.mes-hall↗

arXiv2016

Dispersion laws of the two-dimensional cavity magnetoexciton-polaritons

The energy spectrum of the 2D cavity magnetoexciton-polaritons has been investigated previously, using exact solutions for the Landau quantization of conduction electrons and heavy holes provided by the Rashba method [1]. Two lowest Landau quantization levels for electrons and three lowest Landau levels for heavy-holes, lead to the construction of the six lowest magnetoexciton sates. They consist of two dipole-active, two quadrupole-active, and the two forbidden quantum transitions from the ground state of the crystal to the magnetoexciton states. The interaction of the four optical-active magnetoexciton states with the cavity mode photons with a given circular polarization and with well-defined incidence direction leads to the creation of five magnetoexciton-polariton branches. The fifth order dispersion equation is examined by using numerical calculations and the second order dispersion equation is solved analytically, taking into account only one dipole-active magnetoexciton state. The effective polariton mass on the lower polariton branch, the Rabi frequency and the corresponding Hopfield coefficients are determined in dependence on the magnetic field strength, the Rashba spin-orbit coupling parameters and the electron and hole g-factors.

cond-mat.quant-gas↗

arXiv2015

Radiation Heat Transfer in Particle-Laden Gaseous Flame: Flame Acceleration and Triggering Detonation

In this study we examine influence of the radiation heat transfer on the combustion regimes in the mixture, formed by suspension of fine inert particles in hydrogen gas. The gaseous phase is assumed to be transparent for the thermal radiation, while the radiant heat absorbed by the particles is then lost by conduction to the surrounding gas. The particles and gas ahead of the flame is assumed to be heated by radiation from the original flame. It is shown that the maximum temperature increase due to the radiation preheating becomes larger for a flame with lower velocity. For a flame with small enough velocity temperature of the radiation preheating may exceed the crossover temperature, so that the radiation heat transfer may become a dominant mechanism of the flame propagation. In the case of non-uniform distribution of particles, the temperature gradient formed due to the radiation preheating can initiate either deflagration or detonation ahead of the original flame via the Zel'dovich's gradient mechanism. The initiated combustion regime ignited in the preheat zone ahead of the flame depends on the radiation absorption length and on the steepness of the formed temperature gradient. Scenario of the detonation triggering via the temperature gradient mechanism formed due to the radiation preheating is plausible explanation of the transition to detonation in Supernovae Type Ia explosion.

physics.flu-dyn↗

arXiv2015

Two-dimensional cavity polaritons under the influence of the perpendicular strong magnetic and electric fields. The gyrotropy effects

The properties of the two-dimensional cavity polaritons subjected to the action of a strong perpendicular magnetic and electric fields, giving rise to the Landau quantization (LQ) of the 2D electrons and holes accompanied by the Rashba spin-orbit coupling, by the Zeeman splitting and by the nonparabolicity of the heavy-hole dispersion law are investigated. We use the method proposed by Rashba [1] and the obtained results are based on the exact solutions for the eigenfunctions and for the eigenvalues of the Pauli-type Hamilonians with third order chirality terms and nonparabolic dispersion law for heavy-holes and with the first order chirality terms for electrons. The selection rules of the band-to-band optical quantum transitions as well as of the quantum transitions from the ground state of the crystal to the magnetoexciton states depend essentially on the numbers $n_{e}$ and $n_{h}$ of the LQ levels of the (e-h) pair forming the magnetoexciton. It is shown that the Rabi frequency $Ω_{R}$ of the polariton branches and the magnetoexciton oscillator strength $f_{osc}$ increase with the magnetic field strength $B$ as $Ω_{R}\sim \sqrt{B}$, and $f_{osc}\sim B$. The optical gyrotropy effects may be revealed changing the sign of the photon circular polarization at a given sign of the wave vector longitudinal projection $k_{z}$ or eqivalently changing the sign of $k_{z}$ at the same selected circular polarization.

cond-mat.quant-gas↗

arXiv2015

Ignition of Deflagration and Detonation Ahead of the Flame due to Radiative Preheating of Suspended Micro Particles

We study a flame propagating in the gaseous combustible mixture with suspended inert particles. The gas is assumed to be transparent for the radiation emitted by the combustion products, while particles absorb and re-emit the radiation. Thermal radiation heats the particles, which in turn transfer the heat to the surrounding gaseous mixture by means of heat conduction, so that the gas temperature lags that of the particles. We consider different scenarios depending on the spatial distribution of the particles, their size and the number density. In the case of uniform distribution of the particles the radiation causes a modest increase of the temperature ahead of the flame and the corresponding increase of the flame velocity. The effects of radiation preheating is stronger for a flame with smaller normal velocity. In the case of non-uniform distribution of the particles, such that the particles number density is smaller just ahead of the flame and increases in the distant region ahead of the flame, the preheating caused by the thermal radiation may trigger additional independent source of ignition. This scenario requires the formation of a temperature gradient with the maximum temperature sufficient for ignition in the region of denser particles cloud ahead of the advancing flame. Depending on the steepness of the temperature gradient formed in the unburned mixture, either deflagration or detonation can be initiated via the Zeldovich's gradient mechanism. The ignition and the resulting combustion regimes depend on the temperature profile which is formed in effect of radiation absorption and gas-dynamic expansion. In the case of coal dust flames propagating through a layered dust cloud the effect of radiation heat transfer can result in the propagation of combustion wave with velocity up to 1000m/s and can be a plausible explanation of the origin of dust explosion in coal mines.

physics.flu-dyn↗

arXiv2015

Influence of the radiation absorbed by micro particles on the flame propagation and combustion regimes

Thermal radiation of the hot combustion products usually does not influence noticeably the flame propagating through gaseous mixture. the situation is changed drastically in the presence even small concentration of particles, which absorb radiation, transfer the heat to the surrounding unburned gaseous mixture by means of heat conduction, so that the gas phase temperature in front of the advancing flame lags that of the particles. It is shown that radiative preheating of unreacted mixture ahead of the flame results in a modest increase of the advancing flame velocity for a highly reactive gaseous fuel, or to considerable increase of the flame velocity in the case of a slow reactive mixture. The effects of radiation preheating as stronger as smaller the normal flame velocity. The radiation heat transfer can become a dominant mechanism compared with molecular heat conduction, determining the structure and the speed of combustion wave in the case of a small enough velocity of the advancing flame. It is shown that in the case of non-uniform distribution of the particles, such that time of the radiation heating is longer so that the maximum temperature in the region of denser particles cloud ahead of the advancing flame is sufficient for ignition, the thermal radiation may trigger additional independent source of ignition. Depending on the steepness of the temperature gradient formed in the unburned mixture, either deflagration or detonation can be initiated via the Zeldovich's gradient mechanism. Ignition of different combustion regimes, depending on the radiation absorption length, is illustrated for the particle-laden hydrogen-oxygen flame.

physics.flu-dyn↗

arXiv2014

Landau quantization, Rashba spin-orbit coupling and Zeeman splitting of two-dimensional heavy holes

The origin of the g-factor of the two-dimensional (2D) electrons and holes moving in the periodic crystal lattice potential with the perpendicular magnetic and electric fields is discussed. The Pauli equation describing the Landau quantization accompanied by the Rashba spin-orbit coupling (RSOC) and Zeeman splitting (ZS) for 2D heavy holes with nonparabolic dispersion law is solved exactly. The solutions have the form of the pairs of the Landau quantization levels due to the spinor-type wave functions. The energy levels depend on amplitudes of the magnetic and electric fields, on the g-factor {g-h}, and on the parameter of nonparabolicity C. The dependences of two energy levels in any pair on the Zeeman parameter {Z_h}={g_h}{m_h}/4{m_0}, where {m_h} is the hole effective mass, are nonmonotonous and without intersections. The smallest distance between them at C=0 takes place at the value {Z_h}=n/2, where n is the order of the chirality terms determined by the RSOC and is the same for any quantum number of the Landau quantization.

cond-mat.str-el↗

arXiv2014

Bose-Einstein Condensation of two-dimensional polaritons in microcavity under the influence of the Landau quantization and Rashba spin-orbit coupling

The Bose-Einstein condensation (BEC) of the two-dimensional (2D) magnetoexciton-polaritons in microcavity, when the Landau quantization of the electron and hole states accompanied by the Rashba spin-orbit coupling plays the main role, were investigated. The Landau quantization levels of the 2D heavy holes with nonparabolic dispersion law and third order chirality terms both induced by the external electric field perpendicular to the semiconductor quantum well as the strong magnetic field B gives rise to the nonmonotous dependence on B of the magnetoexciton energy levels and of the polariton energy branches. The Hamiltonian describing the Coulomb electron - electron and the electron - radiation interactions was expressed in terms of the two-particle integral operators such as the density operators $\hatρ(\vec{Q})$ and $\hat{D}(\vec{Q})$ representing the optical and the acoustical plasmons and the magnetoexciton creation and annihilation operators $Ψ_{ex}^{\dagger}({\vec{k}_{||}}),Ψ_{ex}^{}({\vec{k}_{||}})$ with in - plane wave vectors ${\vec{k}_{||}}$ and $\vec{Q}$. The polariton creation and annihilation operators $L_{ex}^{\dagger}({\vec{k}_{||}}),L_{ex}^{}({\vec{k}_{||}})$ were introduced using the Hopfield coefficients and neglecting the antiresonant terms because the photon energies exceed the energy of the cavity mode. The BEC of the magnetoexciton - polariton takes place on the lower polariton branch in the point ${\vec{k}_{||}}=0$ with the quantized value of the longitudinal component of the light wave vector, as in the point of the cavity mode.

cond-mat.str-el↗

arXiv2013

Validation of reduced kinetic models for simulations of non-steady combustion processes

In the present work we compare reliability of several most widely used reduced detailed chemical kinetic schemes for hydrogen-air and hydrogen-oxygen combustible mixtures. The validation of the schemes includes detailed analysis of 0D and 1D calculations and comparison with experimental databases containing data on induction time, equilibrium temperature, composition of the combustion products, laminar flame speed and the flame front thickness at different pressures. 1D calculations are carried out using the full gasdynamical system for compressible viscous thermal conductive multicomponent mixture. The proper choice of chemical kinetics models is essential for obtaining reliable quantitative and qualitative insight into combustion phenomena such as flame acceleration and stability, ignition, transition from deflagration-to-detonation (DDT) using a multiscale numerical modeling.

physics.flu-dyn↗

arXiv2013

True, quasi and unstable Nambu Goldstone modes of the twodimensional Bose Einstein condensed magnetoexcitons

The collective elementary excitations of two dimensional magnetoexcitons in a Bose Einstein condensate with zero wavevector are investigated in the framework of the Bogoliubov theory of quasi averages. The Hamiltonian of the electrons and holes lying in the lowest Landau levels contains supplementary interactions due to virtual quantum transitions of the particles to the excited Landau levels and back. As a result, the interaction between the magnetoexcitons zero wavenumbers does not vanish and their BEC becomes stable. The energy spectrum contains only one gapless,true Nambu Goldstone mode of the second kind, proportional to the square of wavenumber at small values of wavenumber describing the optical plasmon type oscillations. There are two exciton type branches corresponding to normal and abnormal Green functions. Both modes are gapped with roton type segments at intermediary values of the wavevectors and can be named quasi NG modes. The fourth branch is the acoustical plasmon type mode with absolute instability in the region of small and intermediary values of the wavevectors. All branches have a saturation type dependencies at great values of the wave vectors. The number and the kind of the true NG modes are in accordance with the number of the broken symmetry operators.

cond-mat.mes-hall↗

arXiv2012

Spontaneous symmetry breaking and coherence in two-dimensional electron-hole and exciton systems

The spontaneous breaking of the continuous symmetries of the two-dimensional(2D) electron-hole systems in a strong perpendicular magnetic field leads to the formation of new ground states and determines the energy spectra of the collective elementary excitations appearing over these ground states. In this review the main attention is given to the electron-hole systems forming coplanar magnetoexcitons in the Bose-Einstein condensation(BEC) ground state with the wave vector k=0, taking into account the excited Landau levels, when the exciton-type elementary excitations coexist with the plasmon-type oscillations. At the same time properties of the two-dimensional electron gas(2DEG) spatially separated as in the case of double quantum wells(DQWs) from the 2D hole gas under conditions of the fractional quantum Hall effect(FQHE) are of great interest because they can influence the quantum states of the coplanar magnetoexcitons when the distance between the DQW layers diminishes. We also consider in this review the bilayer electron systems under conditions of the FQHE with the one half filling factor for each layer and with the total filling factor for two layers equal to unity because the coherence between the electron states in two layers is equivalent to the formation of the quantum Hall excitons(QHExs) in a coherent macroscopic state. The breaking of the global gauge symmetry as well as of the continuous rotational symmetries leads to the formation of the gapless Nambu-Goldstone(NG) modes while the breaking of the local gauge symmetry gives rise to the Higgs phenomenon characterized by the gapped branches of the energy spectrum. The conditions in which the spontaneous coherence could appear in a system of indirect excitons in a double quantum well structures are discussed. The experimental attempts to achieve these conditions, the main results and the accumulated knowledge are reviewed.

cond-mat.str-el↗

arXiv2007

Clustering of Aerosols in Atmospheric Turbulent Flow

A mechanism of formation of small-scale inhomogeneities in spatial distributions of aerosols and droplets associated with clustering instability in the atmospheric turbulent flow is discussed. The particle clustering is a consequence of a spontaneous breakdown of their homogeneous space distribution due to the clustering instability, and is caused by a combined effect of the particle inertia and a finite correlation time of the turbulent velocity field. In this paper a theoretical approach proposed in Phys. Rev. E 66, 036302 (2002) is further developed and applied to investigate the mechanisms of formation of small-scale aerosol inhomogeneities in the atmospheric turbulent flow. The theory of the particle clustering instability is extended to the case when the particle Stokes time is larger than the Kolmogorov time scale, but is much smaller than the correlation time at the integral scale of turbulence. We determined the criterion of the clustering instability for the Stokes number larger than 1. We discussed applications of the analyzed effects to the dynamics of aerosols and droplets in the atmospheric turbulent flow.

physics.ao-ph↗