Highly nonlinear excitonic Zeeman spin splitting in composition-engineered artificial atoms

Non-linear Zeeman splitting of neutral excitons is observed in composition engineerd InxGa1-xAS self-assembled quantum dots and its microscopic origin is explained. Eight-band k . p simulations, performed using realistic dot parameters extracted from cross-sectional scanning tunneling microscopy, reveal that a quadratic contribution to the Zeeman energy originates from a spin dependent mixing of heavy and light hole orbital states in the dot. The dilute In-composition (x 0.35) and large lateral size (40 - 50 nm) of the quantum dots investigated is shown to strongly enhance the non-linear excitonic Zeeman gap, providing a blueprint to enhance such magnetic non-linearitics via growth engineerin