Strong coupling of heavy- and light-hole excitons induced by many-body correlations

The differential absorption of a GaAs single quantum well is studied for resonant pumping at either the heavy- or light-hole exciton resonances using different polarization configurations. For all excitation conditions the observed spectra show bleaching of both excitons, revealing strong coupling between the heavy- and light-hole excitons. Microscopic calculations which include four-particle correlations representing the various two-exciton states qualitatively reproduce the experimental findings. A mixed heavy-hole-light-hole biexciton is also clearly identified as an induced resonance in a GaAs system.