Anisotropic hole spins in single and coupled self-assembled quantum dots

Anisotropy of hole spins in single and coupled self-assembled InAs/GaAs quantum dots is studied theoretically by means of an effective bond-orbital method. Compared with isotropic electron spins within the growth plane, it is found that the hole spins, although with much smaller positive g factors, can be highly anisotropic in single quantum dots. It is shown that the in-plane anisotropy of the hole spins can even reverse its sign as the height of the dots varies. In vertically coupled quantum dots, the in-plane hole g factors become comparable to the electrons, almost one order of magnitude larger than those in the single dots. Our result agrees qualitatively with the recent experiment [S. A. Crooker et al., Phys. Rev. Lett. 104, 036601 (2010)].