SPIN-DEPENDENT EXCITON-EXCITON INTERACTIONS IN QUANTUM WELLS

We have investigated the exciton luminescence and polarization dynamics in high-quality ${\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ quantum wells under resonant excitation. Experimental manifestations of exciton-exciton interactions including a spin-dependent luminescence linewidth, a spin-dependent absorption, and a spin-dependent optical dephasing time are evidenced. All the experimental results are interpreted in terms of mutual exciton exchange interaction.