DEPHASING OF EXCITONS IN A CDTE/CD0.86MN0.14TE MULTIPLE-QUANTUM-WELL

The dephasing of heavy- and light-hole excitons in CdTe/Cd0.86Mn0.14Te multiple quantum wells is investigated by means of subpicosecond transient four-wave mixing. We find dephasing times on the order of 2 ps, corresponding to a homogeneous linewidth of 0.65 meV, for the free heavy-hole exciton at 5 K and moderate exciton density. Density and temperature dependent measurements of the homogeneous linewidth allow the determination of the interaction strength for exciton-exciton and exciton-phonon scattering as well as of the residual contribution due to extrinsic scattering processes. Simultaneous excitation of heavy- and light-hole excitons leads to the appearance of quantum beats, allowing the determination of the light-hole dephasing time. We find that the light hole dephases 4-5 times faster than the heavy-hole exciton. This faster dephasing of the light-hole exciton is attributed to a resonant coupling between the ls light-hole and the 2s heavy-hole exciton state. The results are compared to published data for GaAs/Al1-xGaxAs quantum wells.