Nuclear Spin Diffusion Mediated by Heavy Hole Hyperfine Non-Collinear   Interactions
  We show that the hyperfine mediated dynamics of heavy hole states confined in neutral self- assembled quantum dots leads to a nuclear spin diffusion mechanism. It is found that the oftentimes neglected effective heavy hole hyperfine non-collinear interaction is responsible for the low degree of nuclear spin polarization in neutral quantum dots. Moreover, our results demonstrate that after pumping the nuclear spin state is left in a complex mixed state, from which it is not straightforward to deduce the sign of the Ising-like interactions. 
Hugo Ribeiro, Franziska Maier, and Daniel Loss
cond-mat.mes-hall