We present an experimental study of the dynamics underlying the buildup and decay of dynamical nuclear spin polarization in a single semiconductor quantum dot. Our experiment shows that the nuclei can be polarized on a time scale of a few milliseconds, while their decay dynamics depends drastically on external parameters. We show that a single electron can very efficiently depolarize the nuclear spins and discuss two processes that can cause this depolarization. Conversely, in the absence of a quantum dot electron, the lifetime of nuclear spin polarization is on the time scale of a second, most likely limited by the non-secular terms of the nuclear dipole-dipole interaction. We can further suppress this depolarization rate by 1-2 orders of magnitude by applying an external magnetic field exceeding 1 mT.
@article{arxiv.0704.3684,
title = {Dynamics of Quantum Dot Nuclear Spin Polarization Controlled by a Single Electron},
author = {P. Maletinsky and A. Badolato and A. Imamoglu},
journal= {arXiv preprint arXiv:0704.3684},
year = {2007}
}