Dynamic Polarization Of Electron Spins In Indirect Band Gap (In,Al)As/Alas Quantum Dots In A Weak Magnetic Field: Experiment And Theory

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.