In cubic semiconductors such as GaAs under uniaxial strain, we determine the spin–orbit equivalent magnetic field acting on hole spins. This field is the sum of a Dresselhaus-like field caused by the lack of inversion symmetry and of a contribution proportional to the strain. Depending on the strain orientation, along 0 0 1, 1 1 1, or 1¯10, and on whether the holes are heavy or light, three types of novel effects can be predicted: (i) It is possible to suppress the valence spin–orbit interaction for all values of momentum. (ii) By tuning the strain, one can reach a SU(2) symmetry among the heavy or light valence bands, thus opening the possibility to observe a hole-related persistent spin helix. (iii) Finally, for heavy holes under strain along 111 (Z direction), the spin–orbit field lies along Z and only depends on kZ. This implies that the Z component of the hole spin is not affected by spin–orbit-related relaxation, thus leading to an orientation anisotropy of this relaxation. Conversely, for light holes, it is orthoradial in the XY plane, and its length is proportional to the modulus k⊥ of the transverse wave vector.
Amand et al. (Wed,) studied this question.