Mapping hole spin texture in quantum dots and quantum dot molecules

Holes in semiconductor quantum dots (QD) and quantum dot molecules (QDM) have unique electronic and spin properties that make them a promising candidate for a qubit. To understand the physical origin of these properties and identify promising paths to optimizing these properties for device applications, we use atomistic tight binding theory and a finite basis matrix approximation to compute the contributions to hole spin projections at each atomic site within a QD or QDM. We consider strained InAs/GaAs and strain-free GaAs/AlAs QDs and vertically stacked InAs/GaAs QDMs subject to a variety of applied electric and magnetic fields. For example, in a single GaAs/AlAs QD we observe a strong spin polarization in the z-direction with an applied lateral electric field parallel to a Voigt configuration magnetic field. However, the hole spin remains unpolarized when the lateral electric field is orthogonal to the magnetic field. We use a 3-D model to explore the spin contributions from anion and cation sites, different atomic planes, and separate QDs within a QDM. We suggest possible experiments to validate these computational results.