Optical and magnetic anisotropies of the hole states in Stranski-Krastanov quantum dots

Abstract

Using the trion as a monitor we investigate the anisotropy of the single-hole state in epitaxial $\mathrm{Cd}\mathrm{Se}∕\mathrm{Zn}\mathrm{Se}$ quantum dots. Heavy-light hole mixing caused by a symmetry reduction below ${D}_{2\mathrm{d}}$ results in elliptical polarization of the optical transitions with a specific axis for each dot defined by strain and shape. In a transverse magnetic field, a quartet of strictly linearly polarized lines appears that reveals the off-diagonal coupling of both electron and hole states. Although induced by the field, the linear polarization is not related to the field orientation, but either along or perpendicular to the dot axis seen at zero field. We find an in-plane hole $g$ factor as large as 0.3 with distinct anisotropic behavior.