Discovery of a nonstoichiometric Zn 11 MnSe 13 magnetic magic quantum dot from ab initio calculations

TLDR: In this article, a nonstoichiometric magnetic magic ZnSe quantum dots (QDs) doped with one Mn atom were shown to exhibit a new non-stochastic magnetic magic structure.

Abstract: Ab initio calculations on ZnSe quantum dots (QDs) doped with one Mn atom predict a new nonstoichiometric magnetic magic Zn${}_{11}$MnSe${}_{13}$ structure in contrast to QDs of undoped ZnSe that are stoichiometric and exhibit magic behavior for Zn${}_{n}$Se${}_{n}$ with $n$ $=$ 13 and 34. Our results suggest that such doping would lead to a high abundance of only one specie (the magic QD) that would be produced preferentially. The stoichiometric Zn${}_{n\ensuremath{-}1}$MnSe${}_{n}$ QDs have a large magnetic moment of 5 ${\ensuremath{\mu}}_{B}$ that is predominantly localized on the Mn site. However, nonstoichiometic QD has a reduced magnetic moment of 3 ${\ensuremath{\mu}}_{B}$ due to strong covalent bonding of the Mn atom with the excess Se atom and a small gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). Charging this magic QD with two electrons leads to a large HOMO-LUMO gap of 1.8 eV and 5 ${\ensuremath{\mu}}_{B}$ magnetic moment. These results together with calculations on Mn-doped $n$ $=$ 34 QD provide a possible growth mechanism of larger doped QDs and a new ground for understanding such QDs of compound semiconductors.