Hole-mediated ferromagnetism in coupled semimagnetic quantum dots

A comprehensive theory is presented on the tuning of hole states in vertically coupled quantum dots based on diluted magnetic semiconductor and on the spontaneous ferromagnetism induced by the p-d exchange interaction. The characteristics of the ground states can be tuned from usual heavy-hole (hh)-like to light-hole (lh)-like by changing structural parameters. We demonstrate that hh-lh coupling strongly influences the p-d exchange interaction, in such a way that an increasing coupling strength enhances the system magnetization. Single-band effective mass approximation may not provide a correct prediction of ferromagnetism in coupled quantum dots, thus a multiband k.p model was adopted that includes the Mn-hole exchange interaction into the same framework and a self-consistent method of the mean field simulation was used.