Excitons in single and vertically coupled type II quantum dots in high magnetic fields

The ground state properties of an exciton in a type II quantum dot are investigated in the presence of a perpendicular magnetic or electric field. The dot is modelled by a quantum disk with radius R and thickness d in which the electron is confined in the disk whereas the dot acts as an antidot for the hole. For disk-like dots, i.e. d < < 2R, the hole is located above and below the disk, while for pillar-like systems, i.e. d >> 2R, the hole is located at the radial boundary for which angular momentum (l) transitions are predicted with increasing magnetic field. The latter system can also be realized by considering vertically coupled dots with small interdot distance. We found that for a sufficiently large magnetic field the ground state exhibits spontaneous symmetry breaking, which results in a magnetic field induced dipole moment. We found that an applied electric field induces a dipole moment leading to a quasi-linear dependence of the Stark shift on the electric field. For systems with a spontanously broken symmetry the Stark shift exhibits a hysteretic behaviour.