The persistent spin helix in the presence of hyperfine interactions
Abstract
We study the effect of hyperfine interaction in the persistent spin helix (PSH) by investigating the nuclear spin pumping caused by non-equilibrium electron spin dynamics. In the first two chapters we rederive, based on already published literature, the PSH diffusion equation and a formalism for calculating the nuclear spin pumping from non-equilibrium electron spin dynamics. To get some useful insight into the procedure we use, and to show that it actually works, we calculate the nuclear spin pumping in a proof of principle setup in chapter 4. The nuclear spin pumping, and its effects, in the PSH is studied in chapter 5. We find that the lowest-order effect of the nuclear spin polarization stabilizes the electron spin structure. Some higher-order contributions introduce higher-order harmonics, which also rotate the spin structure out of the plane of the helix. The stabilizing effect is considerable when 100 % of the nuclei are polarized. However, for a more realistic nuclear spin polarization, the effect is small.