Fermi-edge singularities and enhanced magnetoexcitons in the optical spectra of GaAs/(Ga,Al)As single quantum wells

Pronounced many-body exciton effects have been observed through photoluminescence in modulation-doped n-type GaAs quantum wells where a near-resonance coincidence exists between a transition involving two-dimensional electrons at the Fermi level in the first conduction subband and an exciton transition from the second conduction subband. Under these conditions, strong and distinct Fermi-edge singularities can be observed near k≊0. A magnetic field induces further enhancement of the effect but also leads to very large, ${\mathit{B}}^{\mathrm{-}1}$-periodic amplitude variations in the photoluminescence, with excursions over 3 orders of magnitude.