Measurements of a fast nuclear-spin dynamics in a single InAs quantum dot with positively charged exciton

X. M. Dou, B. Q. Sun^a, D. S. Jiang, H. Q. Ni and Z. C. Niu

SKLSM, Institute of Semiconductors, CAS - P.O. Box 912, Beijing 100083, China

^a bqsun@semi.ac.cn

Received: 5 January 2012
Accepted: 7 March 2012

Abstract

By using time-resolved spectroscopy with an alternative σ⁺/σ⁻ laser pulse modulation technique, we are able to measure the fast buildup and decay times of the dynamical nuclear-spin polarization at 5 K for a single InAs quantum dot with positively charged exciton. It is shown that the measured buildup and decay times are 0.27 and 0.5 ms, respectively, in the absence of external magnetic field. By applying an external field of 8 mT in parallel to the sample growth direction, the decay time extends to about 5 ms which is induced by optically pumped electron via the hyperfine interaction between the nuclei and the electron. In addition, it is found that the buildup time is independent of the small external field.