Exciton-cyclotron resonance in two-dimensional structures in a strong perpendicular magnetic field and optical orientation conditions

Abstract

The absorption band shapes of the combined optical quantum transitions with creation of the two-dimensional magnetoexcitons and simultaneous excitation of one background electron from its lowest to the first-excited Landau level by circularly polarized radiation under the conditions of optical orientation and spin polarization are investigated. The light absorption in the frame of dipole-active transition is described in the second-order perturbation theory taking into account as the perturbations the electron-photon interaction and the electron-electron Coulomb interaction. The Hamiltonian of the electron-photon interaction depends on the directions of the light propagation and its circular polarization relative to the magnetic field direction and the electron-heavy-hole alignment with regard to the plane of the layer. It is shown that the probability of the combined absorption rate is four times larger if the optically created electron has the same spin projection as the background electrons, compared to the case when the electrons have antiparallel spins. The probability of quantum transition and the absorption band peaks decrease with the increased magnetic field as H-1/2 at a given filling factor v(2). If photocreated electron and hole have the same numbers of the Landau levels, n(e)=n(h), the quantum transitions are dipole active. If these numbers differ by one, the quantum transition is quadrupole active, depends on the projections of the light wave vector on the plane of the layer, and vanishes in the Faraday geometry.