  Avoided crossing of the emission lines of a nearly free positive trion and a
cyclotron replica of an exciton bound to an interface acceptor has been
observed in the magneto-photoluminescence spectra of p-doped GaAs quantum
wells. Identification of the localized state depended on the precise mapping of
the anti-crossing pattern. The underlying coupling is caused by an exciton
transfer combined with a resonant cyclotron excitation of an additional hole.
The emission spectrum of the resulting magnetically tunable coherent state
probes weak localization in the quantum well.
