Manipulation of Dynamic Nuclear Polarization in Gallium Arsenide under periodic optical electron spin pumping

Optically oriented electron spins in gallium arsenide polarize the nuclear spin system through a process called dynamic nuclear polarization. The polarized nuclear system will create an effective magnetic field back onto the electron spin system and affect the Larmor precession frequency. The nuclear polarization can be calculated from the change in electron spin polarization using periodic optical pump probe Kerr rotation measurements[1]. We demonstrate that the coupled electron-nuclear spin systems can be manipulated by varying the excitation energy and sweeping an external magnetic field. These dependencies are corroborated by numerical calculations from a model incorporating optical orientation and the optical Stark effect. This model is justified by its correspondence to our experimental observations and can be used to predict the behavior of the nuclear spin polarization.
1 M. Macmahon, J. Iafrate, M. Dominguez, and V. Sih, Phys. Rev. B 99, 075201 (2019)