DIAMAGNETIC SHIFTS OF QUANTUM WELL EXCITONS IN STRONG MAGNETIC FIELDS APPLIED IN THE WELL PLANES

The behaviour of excitons associated with transitions from the light and heavy hole subbands to the electron subbands has been studied in GaAs-(Ga,Al)As quantum wells, with well widths between 2.2 and 14.5 nm, in strong magnetic fields applied in the plane of the quantum wells. The data are successfully modelled using perturbation theory within an envelope function approximation, enabling the higher subband masses to be deduced : the results are in qualitative agreement with the predictions of pseudopotential calculations. Data taken at low fields with the magnetic field parallel and perpendicular to the well planes also reveal the strong non-parabolicity of the first heavy hole subband close to the decoupled (k=0) limit