Hole-mediated ferromagnetism in coupled semimagnetic quantum dots

Abstract

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 $p\ensuremath{-}d$ 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 $hh\ensuremath{-}lh$ coupling strongly influences the $p\ensuremath{-}d$ 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 $\mathbf{k}.\mathbf{p}$ 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.