Transport and lifetime enhancement of photoexcited spins in GaAs by surface acoustic waves

We demonstrate spin transport and spin lifetime enhancement in GaAs quantum wells induced by the traveling piezoelectric field of a surface acoustic wave (SAW). Spin transport lengths of about 3 mum corresponding to spin relaxation times during transport over 1 ns are observed, which are considerably longer than the exciton spin diffusion lengths in the absence of a SAW. The slow spin relaxation is attributed to a reduced electron-hole exchange interaction, when the carriers are spatially separated by the lateral potential modulation induced by the SAW.