Magnetoexciton in semiconductor concentric double rings

We investigate theoretically the magnetoexciton states in semiconductor concentric quantum double rings using the multi-band effective mass theory. We find that a perpendicular magnetic field can lead to oscillations in the exciton energy which appear as kinks in the magneto-photoluminescence (PL) spectra as the magnetic field increases. The spatial distribution of the exciton over the rings depends sensitively on the thicknesses of the inner and outer rings. The tunneling coupling between the inner and outer rings and the heavy-hole and light-hole mixing results in different anticrossing behaviors. Exciton can be converted into a spatially separated type-II exciton by tuning the thickness, the inner and/or outer ring radius and the magnetic field. We show that this type I–type II transition is reflected in the oscillator strength of the PL spectrum which will be the experimental signature that will provide us with information about the spatial distribution of the exciton.     

Magnetoexcitons in unbalanced double layers

We study theoretically correlations of electrons and holes in unbalanced double-layer electronic systems in strong magnetic fields. Calculations are made using the exact diagonalization and the variational wave function. The ground state of an electron–hole pair in quantized cyclotron orbits possesses an in-plane electric dipole moment, when an electron and a hole are in different Landau orbits with different radii. The resulting attractive interactions between pairs creates the possibility of novel states.     

Detection of lateral composition modulation by magnetoexciton spectroscopy

An experimental signature for detecting spontaneous lateral composition modulation in a (InAs) (GaAs) short period superlattice on a InP substrate based on magnetoexciton spectroscopy is described. We find by aligning the magnetic field in three crystallographic directions, one parallel to and the other two perpendicular to the composition modulation direction, that the magnetoexciton shifts are anisotropic and are a good indicator for the presence of composition modulation.