A novel spin orientation mechanism—dynamic electron spin polarization—has been recently suggested in Phys. Rev. Lett. 125, 156801 (2020). It takes place for unpolarized optical excitation in weak magnetic fields of the order of a few millitesla. In this paper we demonstrate experimentally and theoretically that the dynamic electron spin polarization degree changes sign as a function of time, strength of the applied magnetic field, and its direction. The studies are performed on indirect band-gap (In,Al)As/AlAs quantum dots and their results are explained in the framework of a theoretical model developed for our experimental setting.

• Received 2 June 2021
• Revised 31 July 2021
• Accepted 10 August 2021

DOI:https://doi.org/10.1103/PhysRevB.104.115405