EXCITON SPIN DYNAMICS IN QUANTUM-WELLS

A theory of exciton spin dynamics is given in terms of the exchange sp in-flip mechanism taking full account of the confinement of the quantu m well. Exciton spin relaxation belongs to the motional narrowing clas s, with a characteristic inverse proportionality to the momentum scatt ering time of the exciton center of mass. Analysis of the time depende nce of optical intensities of both circular polarizations, including c ompeting relaxation mechanisms from exciton exchange and from single-p article spin flip into optically inactive states, leads to characteris tic shapes reflecting their relative importance. The calculated well-w idth dependence from our theory of the exciton spin relaxation leads t o polarization intensities in good agreement with measurement. Theoret ical electric and magnetic field dependences have yet to be tested aga inst experiment.