Modeling resonant tuning of hole g-tensors and underlying mechanisms in quantum dot molecules

Hole spins in InAs/GaAs quantum dot molecules (QDMs) show promise as semiconductor spin qubits, as hole states are weakly coupled to nuclear spins. QDMs are desired over single dots for the tunability of molecular states, formed by QD states brought to resonance with applied electric fields. Near resonance, the Zeeman splitting of these molecular hole states can be enhanced or suppressed, providing electrical tuning of the hole g-tensor. The formation and tunability of these states is well observed experimentally. Here, we provide an atomistic tight-binding theory for this tuning of Zeeman splitting to elucidate the mechanism for this enhancement and to identify ways to further manipulate the hole g-tensor. We find that the g-tensor tunability near resonance is explained by a strong enhancement or suppression of coupling between the spatial motion of the hole state and the magnetic field, as described in our theory by a Peierls term. In contrast, there is no change in the hole spin or leakage into the interdot barrier near resonance. Phenomenological modeling suggests that spin-dependent interdot tunneling is the mechanism for the g-tensor tunability. We use our atomistic theory to explore the spatial implications of spin-dependent tunneling to critically assess this mechanism.