Dynamic Polarization of Electron Spins in Indirect Band Gap (In,Al)As/AlAs Quantum Dots in a Weak Magnetic Field: Experiment and Theory

Abstract

A novel spin orientation mechanism - dynamic electron spin polarization - has been recently suggested in Phys. Rev. Lett. 125, 156801 (2020)PRLTAO0031-900710.1103/PhysRevLett.125.156801. 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. © 2021 American Physical Society.