Anisotropy of in-plane hole g factor in CdTe/ZnTe quantum dots

Optical studies of a bright exciton provide only limited information about the hole anisotropy in a quantum dot. In this work we present a universal method to study heavy-hole anisotropy using a dark exciton in a moderate in-plane magnetic field. By analysis of the linear polarization of the dark exciton photoluminescence we identify two distinct contributions to the hole g factor: the anisotropic one resulting in a fixed orientation of the dark exciton polarization for any direction of the magnetic field and the quasi-isotropic contribution, due to which the polarization orientation rotates with the magnetic field, but in the opposite direction. We employ the proposed method for a number of individual self-assembled CdTe/ZnTe quantum dots, demonstrating a variety of behaviors of in-plane hole g factor: from almost fully anisotropic to almost quasi-isotropic. We conclude that, in general, both contributions play an important role and neither contribution can be neglected.