Sizable nuclear spin polarization is pumped in individual InP/GaInP dots in a wide range of external magnetic fields B_ext=0-5T by circularly polarized optical excitation. We observe nuclear polarization of up to ~40% at Bext=1.5T and corresponding to an Overhauser field of ~1.2T. We find a strong feedback of the nuclear spin on the spin pumping efficiency. This feedback, produced by the Overhauser field, leads to nuclear spin bi-stability at low magnetic fields of Bext=0.5-1.5T. We find that the exciton Zeeman energy increases markedly, when the Overhauser field cancels the external field. This counter-intuitive result is shown to arise from the opposite contribution of the electron and hole Zeeman splittings to the total exciton Zeeman energy.
@article{arxiv.0710.2837,
title = {Overhauser effect in individual InP/GaInP dots},
author = {J. Skiba-Szymanska and A. V. Nikolaenko and E. A. Chekhovich and A. I. Tartakovskii and M. N. Makhonin and I. Drouzas and M. S. Skolnick and A. B. Krysa},
journal= {arXiv preprint arXiv:0710.2837},
year = {2011}
}