Dynamic Nuclear Polarization with Single Electron Spins

J. R. Petta, J. M. Taylor, A. C. Johnson, A. Yacoby, M. D. Lukin, C. M. Marcus, M. P. Hanson, A. C. Gossard

Published 2007-09-06, updated 2007-09-07Version 2

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.