Theory of Spin-Dependent Phonon-Assisted Optical Transitions in Silicon

Silicon is an ideal material choice for spintronics devices due to its relatively long spin relaxation time and mature technology. To date, however, there are no parameter-free methods to accurately determine the degree of spin polarization of electrons in silicon. This missing link is established with a theory that provides concise relations between the degrees of spin polarization and measured circular polarization for each of the dominant phonon-assisted optical transitions. The phonon symmetries play a key role in elucidating recent spin injection experiments in silicon.