Spin dynamics and level structure of quantum-dot quantum wells

We have characterized $\mathrm{Cd}\mathrm{S}∕\mathrm{Cd}\mathrm{Se}∕\mathrm{Cd}\mathrm{S}$ quantum-dot quantum wells using time-resolved Faraday rotation (TRFR). The spin dynamics shows that the electron $g$ factor varies as a function of quantum well width and the transverse spin lifetime of several nanoseconds is robust up to room temperature. As a function of probe energy, the amplitude of the TRFR signal shows pronounced resonances, which allow one to identify individual exciton transitions. The resonance energies in the TRFR data are consistent with different exciton transitions in which the electron occupies the conduction-band ground state.