Inelastic light scattering by dipolar excitons

The cross section for inelastic light scattering by a system of spatially indirect excitons is calculated. It is shown that there are two resonant scattering channels, one related to the transitions via the vacuum and the other via the two-exciton states of the crystal, and their contributions to the scattering amplitude cancel each other. As a result, there is no resonance enhancement of light scattering by excitons for photon energies in the vicinity of the band gap.     

Edge magneto-exitons (ring excitons) in antidots

Il Nuovo Cimento D - An opening (antidot) in two-dimensional (2D) electron gas placed in a strong perpendicular magnetic field makes it possible the formation of ring-shaped excitons stemming from...     

Generation of Sound by a Two-Dimensional Gas of Indirect Dipolar Excitons

The generation of acoustic waves by a gas of two-dimensional indirect dipolar excitons irradiated by an electromagnetic wave has been studied by the deformation potential method. It has been shown that an acoustic wave propagating into the interior of the isotropic substrate is generally a superposition of longitudinal and transverse waves. At high frequencies of electromagnetic perturbation, the generated acoustic wave degenerates almost completely into a transverse wave. The amplitudes of both waves have been calculated. Their frequency dependences at temperatures above and below the temperature of condensation of the exciton gas have been determined.     

Spin-dependent localization of electrons in low-dimensional systems

Possibilities of spatial localization of spin-polarized electrons due to spin–orbit interaction are investigated theoretically. Situations most interesting for us are the ones where electrons of one spin state (helicity) are localized while the opposite helicity relates to extended wave functions. On examples of simplest short range potentials it is shown that such spin separation is, in principle, possible. Magnetic properties of electrons bound to a shallow 2D axially symmetric well are considered. Accounting for the spin–orbit contribution results in an anomalously large effective g-factor of this system.     

Interaction, damping and possible amplification of 2D plasmons in asymmetric bilayer structures

It is shown that the asymmetry of a double quantum well structure considerably affects the dispersion relations for the optical and intersubband plasmons. A specific mechanism of the plasmon damping arises due to a resonance of the plasmon energy and that of single-particle intersubband transitions. If the population of the subbands is inverted, an amplification of the plasma waves becomes possible.     

Plasma oscillations in a two-dimensional semimetal

Collective oscillations of an electron-hole plasma in a two-dimensional semimetal have been investigated. It has been shown that two undamped branches of plasma oscillations exist under certain conditions on the parameters of the structure. Acoustic plasmons are not damped in a finite wavenumber range. When the Fermi velocities of the electrons and holes are equal to each other, this range expands to the range of the applicability of the theory (the momentum of the plasmon is much lower than the Fermi momenta of the particles).     

Magnetoplasma oscillations in a 2D electron system with spin-orbit interaction

The magnetoplasmon spectrum in a 2D electron plasma is investigated theoretically taking into account the spin—orbit interaction in the Rashba model. The expression is derived for the polarization operator in the semiclassical range of magnetic fields (in which the Fermi energy eF is much larger than the Landau quantum). Approximate analytic formulas are obtained for spin—plasmon branches. The dependences of plasma wave frequencies on the wavevector and magnetic field are calculated from a numerical solution of the dispersion equation. In addition, the magnetic field and frequency dependences of the plasmon absorption intensity are constructed. The absorption intensity at the peak is found to be sensitive to the spin—orbit interaction constant.     

Screening of static perturbation in a system of dipole excitons

The screening of local electrostatic perturbation by indirect excitons has been investigated. It has been shown that the linear screening is dielectric, and the effective dielectric constant may be large in the case of high degeneracy of the Bose gas of excitons. The emergence of a condensate significantly changes the behavior of the perturbation potential at infinity, leading to power-law asymptotic behavior with large exponents. In the nonlinear regime, the screened potential is saturated with an unlimited increase in the initial perturbation.     

Aharonov-Bohm effect for plasmons in a finite-width quantum ring

The magnetoplasma oscillation frequencies of the 2D electrons in a quantum ring have been found taking into account the finite width of the ring in the model allowing for an exact solution for the single-particle spectrum. It is shown that instead of the periodic oscillations of the plasmon frequency ω typical of the 1D ring, ω in the case under consideration depends on the magnetic flux with the frequency and amplitude modulations: the period of oscillations as a function of the magnetic flux and their amplitude depend on the magnetic field strength.     

Spin-magnetoplasma waves in a 2D electron system

Oscillations of a 2D electron plasma in a transverse magnetic field have been theoretically studied taking into account spin-orbit interaction. Four branches of spin-plasmon oscillations associated with different selection rules for spin and orbital quantum numbers have been shown to appear at a small plasmon momentum in a semiclassical limit (the Fermi energy is much higher than the Landau quantum). In the quantum case (the filling factor ν is about unity), the number of branches changes from three to six depending on ν value.