Effect of a uniaxial strain on cubic semiconductors: Toward control of the hole spin–orbit interaction

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.