Spill relaxation and spin-dependent exciton interactions in ZnSe quantum wells

We demonstrate the mutual influence of the dynamics in the real-space and t he spin Darts of the exciton wavefunction evoked by the exchange interactio n. In the regime of high exciton density, the exciton-exciton interaction i n ZnSe/ZnMgSSe quantum wells is found to be: strongly affected by the excit on spin orientation and the longitudinal spin relaxation via single-fermion spin flips. The exciton's homogeneous linewidth as deduced front degenerat e four-wave mixing with prepulse is significantly enhanced in spin-pure exc iton populations by scattering including fermionic exchange. The transverse spin relaxation in the low-density limit is deduced from the decay of spil l quantum-beats in photoluminescence experiments. We find an anti-proportio nality between the spin relaxation and the optical dephasing times. The tem perature dependence of both relaxation times is determined by the exciton-p honon interaction. The latter gradually reduces the electron-hole exchange coupling which is the dominating term in the exciton's transverse spin rela xation. (C) 2000 Elsevier Science B.V. All rights reserved.