Charged two-dimensional magnetoexciton and two-mode squeezed vacuum states

A novel unitary transformation of the Hamiltonian that allows one to partially separate the center-of-mass motion for charged electron-hole systems in a magnetic field is presented. The two-mode squeezed oscillator states that appear at the intermediate stage of the transformation are used for constructing a trial wave function of a two-dimensional (2D) charged magnetoexciton.Comment: 9 pages, 1 figur

Charged mobile complexes in magnetic fields: A novel selection rule for magneto-optical transitions

The implications of magnetic translations for internal optical transitions of charged mobile electron-hole ($e$--$h$) complexes and ions in a uniform magnetic field $B$ are discussed. It is shown that transitions of such complexes are governed by a novel exact selection rule. Internal intraband transitions of two-dimensional (2D) charged excitons $X^-$ in strong magnetic fields are considered as an illustrative example.Comment: 4 pages, 2 figure

Two-dimensional magnetoexcitons in the presence of spin-orbit coupling

We study theoretically the effect of spin-orbit coupling on quantum well excitons in a strong magnetic field. We show that, in the presence of an in-plane field component, the excitonic absorption spectrum develops a double-peak structure due to hybridization of bright and dark magnetoexcitons. If the Rashba and Dresselhaus spin-orbit constants are comparable, the magnitude of splitting can be tuned in a wide interval by varying the azimuthal angle of the in-plane field. We also show that the interplay between spin-orbit and Coulomb interactions leads to an anisotropy of exciton energy dispersion in the momentum plane. The results suggest a way for direct optical measurements of spin-orbit parameters.Comment: 9 pages, 6 figure

Goldstone Mode Relaxation in a Quantum Hall Ferromagnet due to Hyperfine Interaction with Nuclei

Spin relaxation in quantum Hall ferromagnet regimes is studied. As the initial non-equilibrium state, a coherent deviation of the spin system from the ${\vec B}$ direction is considered and the breakdown of this Goldstone-mode state due to hyperfine coupling to nuclei is analyzed. The relaxation occurring non-exponentially with time is studied in terms of annihilation processes in the "Goldstone condensate" formed by "zero spin excitons". The relaxation rate is calculated analytically even if the initial deviation is not small. This relaxation channel competes with the relaxation mechanisms due to spin-orbit coupling, and at strong magnetic fields it becomes dominating.Comment: 8 page

Charged Many-Electron -- Single Hole Complexes in a Double Quantum Well near a Metal Plate

It has been shown that the presence of a metal plate near a double quantum well with spatially separated electron and hole layers may lead to a drastic reconstruction of the system state with the formation of stable charged complexes of several electrons bound to a spatially separated hole. Complexes of both the Fermi and the Bose statistics may coexist in the ground state and their relative densities may be changed with the change of the electron and hole densities. The stability of the charged complexes may be increased by an external magnetic field perpendicular to the layers plane.Comment: to appear in Phys.Rev.Lett. 77, No.7 (1996). 4 pages, RevTeX, 1 figur

Magnetic field dependence of the energy of negatively charged excitons in semiconductor quantum wells

A variational calculation of the spin-singlet and spin-triplet state of a negatively charged exciton (trion) confined to a single quantum well and in the presence of a perpendicular magnetic field is presented. We calculated the probability density and the pair correlation function of the singlet and triplet trion states. The dependence of the energy levels and of the binding energy on the well width and on the magnetic field strength was investigated. We compared our results with the available experimental data on GaAs/AlGaAs quantum wells and find that in the low magnetic field region (B<18 T) the observed transition are those of the singlet and the dark triplet trion (with angular momentum $L_z=-1$), while for high magnetic fields (B>25 T) the dark trion becomes optically inactive and possibly a transition to a bright triplet trion (angular momentum $L_z=0$) state is observed.Comment: 9 pages, 10 figures submitted to Phys. Rev.

Spin polarization and magneto-luminescence of confined electron-hole systems

A BCS-like variational wave-function, which is exact in the infinite field limit, is used to study the interplay among Zeeman energies, lateral confinement and particle correlations induced by the Coulomb interactions in strongly pumped neutral quantum dots. Band mixing effects are partially incorporated by means of field-dependent masses and g-factors. The spin polarization and the magneto-luminescence are computed as functions of the number of electron-hole pairs present in the dot and the applied magnetic field.Comment: To appear in Phys. Rev.

Interaction potential between dynamic dipoles: polarized excitons in strong magnetic fields

The interaction potential of a two-dimensional system of excitons with spatially separated electron-hole layers is considered in the strong magnetic field limit. The excitons are assumed to have free dynamics in the $x$-$y$ plane, while being constrained or `polarized' in the $z$ direction. The model simulates semiconductor double layer systems under strong magnetic field normal to the layers. The {\em residual} interaction between excitons exhibits interesting features, arising from the coupling of the center-of-mass and internal degrees of freedom of the exciton in the magnetic field. This coupling induces a dynamical dipole moment proportional to the center-of-mass magnetic moment of the exciton. We show the explicit dependence of the inter-exciton potential matrix elements, and discuss the underlying physics. The unusual features of the interaction potential would be reflected in the collective response and non-equilibrium properties of such system.Comment: REVTEX - 11 pages - 1 fi