The electron-spin dynamics of positively charged excitons in a single InAs quantum dot (QD) were measured by time-resolved photoluminescence spectroscopy. Using alternating σ${}^{+}/$σ${}^{-}$ pulse sequences to excite the QD, the lattice nuclear spins remained randomly oriented. This method enables us to check the theory of electron-spin relaxation in the randomly distributed frozen fluctuation of the nuclear field. The experimental results are in qualitative agreement with theoretical prediction, showing that the electron-spin polarization decreases to a minimum value at first, and then increases again up to a steady value of about 1/3 of its initial value.

• Received 22 April 2011

DOI:https://doi.org/10.1103/PhysRevB.84.033302