Long nuclear spin decay times controlled by optical pumping in individual quantum dots

Makhonin, M. N.
Tartakovskii, A. I.
Drouzas, I.
Van'kov, A. B.
Wright, T.
Skiba-Szymanska, J.
Russell, A.
Fal'ko, V. I.
Skolnick, M. S.
Liu, H. -Y.
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Nuclear polarization dynamics are measured in the nuclear spin bi-stability 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 non-linear nuclear spin dynamics. We measure nuclear spin decay times in the range 0.2-5 sec, 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 (>5sec) pumping times. The time-resolved methods allow the detection of the unstable nuclear polarization state in the bi-stability regime otherwise undetectable in cw experiments.
Comment: 4 pages, 3 figures, submitted to PRL
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science