ABSTRACT
Two types of linear-k terms in the Hamiltonian were discussed in Chapter 1. One stems from the non-relativistic kp-interaction and thus plays no role in the spintronic properties of the material. The other one, given in Eq. (1.50), originates from spin-orbit interaction in bulk crystals and will be discussed here in more detail. The coupling between electron spin and momentum affects
the energy spectrum in two ways: It creates a spin-orbit split-off band twofold-degenerate in spin projection, as explained in Chapter 1 (Fig. 1.3), and it may generate additional linear and cubic momentum-dependent terms that lift spin degeneracy. Energy splitting that preserves spin degeneracy determines the rate of the Elliot-Yaffet spin relaxation that is the spin-flip-induced randomization of spin alignment in the course of momentum scattering. Linear and cubic spin splitting are at the origin of the Dyakonov-Perel spin relaxation mechanism [1] and also of electric dipole spin resonance (EDSR) that is induced by ac-electric field optical spin-flip transitions between two spin states [2, 3]. The spin-splitting terms in the Hamiltonian will be considered below.
