Spin ordering in magnetic quantum dots: From core-halo to Wigner molecules

The interplay of confinement and Coulomb interactions in quantum dots can lead to strongly correlated phases differing qualitatively from the Fermi liquid behavior. We explore how the presence of magnetic impurities in quantum dots can provide additional opportunities to study correlation effects and the resulting ordering in carrier and impurity spins. By employing exact diagonalization we reveal that seemingly simple two-carrier quantum dots lead to a rich phase diagram. We propose experiments to verify our predictions; in particular, we discuss interband optical transitions as a function of temperature and magnetic field.