We polarize nuclear spins in a GaAs double quantum dot by controlling two-electron spin states near the anti-crossing of the singlet (S) and m_S=+1 triplet (T+) using pulsed gates. An initialized S state is cyclically brought into resonance with the T+ state, where hyperfine fields drive rapid rotations between S and T+, 'flipping' an electron spin and 'flopping' a nuclear spin. The resulting Overhauser field approaches 80 mT, in agreement with a simple rate-equation model. A self-limiting pulse sequence is developed that allows the steady-state nuclear polarization to be set using a gate voltage.
@article{arxiv.0709.0920,
title = {Dynamic Nuclear Polarization with Single Electron Spins},
author = {J. R. Petta and J. M. Taylor and A. C. Johnson and A. Yacoby and M. D. Lukin and C. M. Marcus and M. P. Hanson and A. C. Gossard},
journal= {arXiv preprint arXiv:0709.0920},
year = {2009}
}
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