Optical spin orientation in strained Ge/SiGe quantum wells: A tight-binding approach

We present a theoretical investigation of electron-spin optical orientation in strained Ge/SiGe quantum wells. The atomistic $s{p}^3{d}^5{s}^{\ast }$ nearest-neighbor tight-binding model adopted, allows us to obtain the spin polarization of the excited electrons, as a function of frequency and direction of the incident radiation, in the presence of external fields, different strain conditions, and taking into account contributions arising from states out of the Brillouin zone center. Orbital projected densities of states further highlight spin mixing of the localized spin-orbitals composing the states involved in the optical transitions. Our results illustrate the potential of the adopted method as a theoretical tool to support experiments on optical manipulation of spins in group IV based heterostructures.