Electronic and Magnetic Properties of Manganese Doped Quantum Dots

Abstract

In semiconductor quantum dots electrons and holes are confined in all three spatial directions. Their eigenstates can be tailored by the use of appropriate materials, the size and the shape of the dot and also by applied electric and magnetic fields. When we dope the quantum dot with atoms possessing a large magnetic moment, like manganese, they interact with the electrons or holes via pd exchange interaction. In III-V semiconductors such as GaAs or InAs the Mn atom is an acceptor. So, holes will be the main charge carriers. The interaction of holes with the magnetic manganese impurities is stronger than the interaction of electrons from the conduction band. We calculate numerically the eigenstates of several holes in a quantum dot using k · p theory, under the influence of a magnetic field fully taking into account their Coulomb interaction. The direct interaction between several manganese atoms is very short ranged and, therefore, can be neglected for sufficiently separated magnetic impurities. An interaction, however, is mediated by the holes confined in the quantum dot. We examine the possibility to control the alignment of several manganese atoms in GaAs and InAs quantum dots by changing the hole eigenstates via a manipulation of the confining potentials and the magnetic field. We show the high importance of the hole-band mixing to the Coulomb energy of up to three holes. It also significantly influences the dispersion of the hole in the magnetic field and the coupling between the spins of the hole and the manganese impurity. We show the influence of the acceptor potential in dependence of the strength of the different dot-potential configurations. In magnetic fields the properties of the hole- and manganese-spin compound coupled by the pdinteraction are dominated in GaAs dots by the manganese spin whereas in InAs the spin of the hole is dominant. Finally we demonstrate the control of the ferromagnetic Mn-Mn coupling by the number of the confined holes.