Direct observation of relaxation dynamics of spin-polarized electrons excited at a higher-energy spin-split subband in a diluted magnetic semiconductor quantum well.

The authors observe relaxation dynamics of spin-polarized electrons excited at a higher-energy spin-split subband in a diluted magnetic semiconductor quantum well by means of pump-probe absorption spectroscopy. Time dependences of the circularly polarized saturated absorbance directly show the relaxation of spin-polarized electrons, which is inaccessible by photoluminescence. The probe-energy dependence of the relaxation time is obtained ranging from 2 to 100 ps at 2.5 T within the absorption band. This dependence is systematically explained by both the intraband energy relaxation of the spin-polarized electrons and the subsequent electron-spin relaxation that is modified by effects of the exciton localization. [ABSTRACT FROM AUTHOR]