The optical spin orientation and subsequent dynamic nuclear polarization (DNP) in individual self-assembled InGaAs/GaAs quantum dots doped by a single Mn atom is shown to be strongly perturbed by the exchange interaction between a photo-created electron and the spin of the magnetic impurity.
The anisotropic part of the exchange, if strong enough, significantly depolarizes the electron spin in moderate magnetic fields, preventing thus any DNP. Yet, for small anisotropies, a pronounced DNP develops in an external magnetic field and shows a remarkable succession of rises interrupted by abrupt falls (evidenced by spectral jumps in the magneto-PL image).
This striking behavior reveals the contribution of the exchange interactions to the energy cost of electron-nucleus spin flip-flops which drives the DNP efficiency.
Reference:
Exchange interaction-driven dynamic nuclear polarization in Mn-doped InGaAs/GaAs quantum dots,
O. Krebs, E. Baudin, & A. Lemaître
Physical Review B 94, 195412 (2016) / DOI : https://doi.org/10.1103/PhysRevB.94.195412
