Spin dynamics of carriers and excitons in nanostructure diluted magnetic semiconductors

Spin dynamics of carriers and excitons are studied in nanostructure diluted magnetic semiconductors (DMSs), in which the carrier spins are highly polarized due to the giant Zeeman effects. Spin injection and spatial spin separation are demonstrated in coupled double quantum wells (DQWs) composed of the DMS and non-magnetic wells. Individual spin-polarized tunnelings of electrons and heavy holes (hhs) through a tunneling barrier are directly observed by pump-probe absorption spectroscopy. The spin separation of hhs is realized in a magnetic DQW without a barrier, which is confirmed as a spin-dependent type-II radiative recombination of the excitons. The spin injections are demonstrated in coupled quantum disks fabricated by electron-beam lithography and also in self-assembled quantum dots (SAQDs) coupled with a DMS quantum well. In the coupled SAQD system, efficient spin injection is realized via resonant spin tunneling assisted by LO-phonon scattering.