Cyclotron‐Assisted Resonant Exciton Exchange Between Nearly‐Free and Acceptor‐Bound States of a Positive Trion

We report detection of the coupling of two different radiative states in magneto‐photoluminescence spectra of a two‐dimensional hole gas in a GaAs quantum well. The pair of coupled states are an acceptor‐bound trion $AX+$ and an essentially free (only weakly localized by a shallow lateral potential) trion $X+,$ brought into resonance by an additional cyclotron excitation controlled by the magnetic field. The coupling mechanism is the exciton transfer, and the optical signature is a clear anticrossing of the emission lines of an $X+$ and a cyclotron replica of the $AX+.$