We show that a magnetic field perpendicular to an AlGaAs/GaAs coupled quantum well efficiently traps dipolar excitons and leads to the stabilization of the excitonic formation and confinement in the illumination area. Hereby, the density of dipolar e
xcitons is remarkably enhanced up to $sim 10^{11} cm^{-2}$. By means of Landau level spectroscopy we study the density of excess holes in the illuminated region. Depending on the excitation power and the applied electric field, the hole density can be tuned over one order of magnitude up to $sim 2.5$ $10^{11} cm^{-2}$ - a value comparable with typical carrier densities in modulation-doped structures.
We investigate exciton spin memory in individual InAs/GaAs self-assembled quantum dots via optical alignment and conversion of exciton polarization in a magnetic field. Quasiresonant phonon-assisted excitation is successfully employed to define the i
nitial spin polarization of neutral excitons. The conservation of the linear polarization generated along the bright exciton eigenaxes of up to 90% and the conversion from circular- to linear polarization of up to 47% both demonstrate a very long spin relaxation time with respect to the radiative lifetime. Results are quantitatively compared with a model of pseudo-spin 1/2 including heavy-to-light hole mixing.
We conduct a series of magnetohydrodynamical (MHD) simulations of magnetized interstellar medium (ISM) disturbed by exploding stars. Each star deposits a randomly oriented, dipolar magnetic field into ISM. The simulations are performed in a Cartesian
box, in a reference frame that is corotating with the galactic disk. The medium is stratified by vertical galactic gravity. The resulting turbulent state of ISM magnetized by the stellar explosions is processed with the aid of Fourier analysis. The results leads to the conclusion that the input of magnetic energy from exploding stars is additionally multiplied by differential rotation. The resulting magnetic field appears to grow up in small-scale component, while the total magnetic flux remains limited. Our results indicate that magnetic field originating from exploding stars can be a source of initial magnetic fields for a subsequent dynamo process.
