COHERENT SPIN DYNAMICS OF ELECTRONS IN II-VI SEMICONDUCTOR QUANTUM WELLS

Coherent spin dynamics of electrons and holes is studied experimentally in CdTe/Cd 0.78 Mg 0.22 Te quantum wells with a two-dimensional electron gas of low density. A picosecond pump-probe Kerr rotation and time-resolved polarized photoluminescence detected by a streak camera are used as experimental techniques. Strong Coulomb interaction between electrons and holes, which results in large binding energies of neutral and negatively charged excitons (trions), allows selective addressing of exciton and trion states with resonant optical excitation. Spin dephasing time of electrons up to 30 ns is achieved at a low temperature of 1.9 K and in a zero magnetic field limit. It decreases for higher lattice temperatures and with increase of excitation density. Spin relaxation times for exciton of 65 ps and trion of 25 ps have been measured under quasi-resonant excitation of excitons.