A. V. Kalameitsev

Excitons in quantum-ring structures in a magnetic field: optical properties and persistent currents

We study theoretically the magnetic-#eld e1ect on a neutral, but polarizable exciton con#ned in quantum-ring structures. For excitons with a nonzero dipole moment, a novel magnetic interference e1ect occurs: The ground state of an exciton con#ned in a #nite-width quantum ring possesses a nonzero angular momentum with increasing normal magnetic #eld. This e1ect is accompanied by a suppression of the photoluminescence in well-de#ned magnetic-#eld intervals. The magnetic interference e1ect is calculated for type-II quantum dots and quantum rings. ? 2002 Elsevier Science B.V. All rights reserved.

Nonlinear acoustoelectric transport in a two-dimensional electron system

We study both theoretically and experimentally the nonlinear interaction between an intense surface acoustic wave and a two-dimensional electron plasma in semiconductor-piezocrystal hybrid structures. The experiments on hybrid systems exhibit strongly nonlinear acoustoelectric effects. The plasma turns into moving electron stripes, the acoustoelectric current reaches its maximum, and the sound absorption strongly decreases. To describe the nonlinear phenomena, we develop a coupled-amplitude method for a two-dimensional system in the strongly nonlinear regime of interaction. At low electron densities the absorption coefficient decreases with increasing sound intensity, whereas at high electron density the absorption coefficient is not a monotonous function of the sound intensity. High-harmonic generation coefficients as a function of the sound intensity have a nontrivial behavior. Theory and experiment are found to be in a good agreement.

Magnetoexcitons in quantum-ring structures: a novel magnetic interference effect

Abstract A novel magnetic interference effect is proposed for a neutral, but polarizable exciton in a quantum ring with a finite width. The magnetic interference effect originates from the nonzero dipole moment in the exciton. The ground state of exciton acquires a nonzero angular momentum with increasing normal magnetic field. This leads to the suppression of the photoluminescence in defined windows of the magnetic field.

Enhancement of the Nonlinear Acoustoelectric Interaction in a Photoexcited Plasma in a Quantum Well

Nonlinear interaction of an intense surface acoustic wave (SAW) with a 2D electron-hole plasma generated by light in a semiconductor quantum well near a piezoelectric crystal is investigated. It is shown that, in a strongly nonlinear regime, the acoustoelectric interaction is enhanced because of the accumulation of carriers in the field of an intense SAW. In addition, in a strongly nonlinear regime, the dissipation of the acoustic wave energy increases and the sound velocity decreases. These dependences fundamentally differ from those observed in a unipolar plasma. For high sound intensities, analytical results are obtained.

Polaron in an electron–exciton structure under the conditions of the Bose–Einstein condensation

A polaron state of an electron in a hybrid system composed of a two-dimensional electron gas and a Bose–Einstein condensate of excitons situated in a quantum well coplanar with the electron gas has been investigated. It has been shown that self-localization is possible even at a weak coupling between the components of the structure, when a fluctuation of the density of excitons producing a potential well for the electron is small compared to their average density.

Magnetoexcitons in core/shell quantum dots

The ground-state energies of the “bright” and “dark” excitons formed by an electron and a hole localized in a thin spherical shell subjected to a high magnetic field are calculated. This model corresponds to a core/shell quantum dot. The high-field condition implies that the magnetic length is much shorter than the radius of the sphere. It is found that the ground-state energy of the bright exciton exhibits an unusual magnetic-field dependence: E0 ∼ H2/3.

Maxwell relaxation of excitons in double quantum wells

The spreading of dipolar excitons in double quantum wells is described by a nonlinear continuity equation. It has been shown that the law of corresponding states holds, which allows one to find the dependence of the characteristic process parameters on the amplitude and width of the initial distribution. In contrast to usual (linear) diffusion, the spreading occurs much faster in the one-dimensional case than in the two-dimensional case.