Makhonin, M. N. and Tartakovskii, A. I. and Van'kov, A. B. and Drouzas, I. and Wright, T. and Skiba-Szymanska, J. and Russell, A. and Falko, Vladimir and Skolnick, M. S. and Liu, H. -Y. and Hopkinson, M. (2008) Long nuclear spin polarization decay times controlled by optical pumping in individual quantum dots. Physical review B, 77 (12): 125307. ISSN 1098-0121
Abstract
Nuclear polarization dynamics are measured in the nuclear spin bistability regime in a single optically pumped InGaAs/GaAs quantum dot. The controlling role of nuclear spin diffusion from the dot into the surrounding material is revealed in pump-probe measurements of the nonlinear nuclear spin dynamics. We measure nuclear spin polarization decay times in the range of 0.2-5 s, strongly dependent on the optical pumping time. The long nuclear spin decay arises from polarization of the material surrounding the dot by spin diffusion for long (>5s) pumping times. The time-resolved methods allow the detection of the unstable nuclear polarization state in the bistability regime otherwise undetectable in cw experiments.