Effect of an impurity on 3-electron quantum dots in magnetic fields

The ground-state property of a 2-dimensional 3-electron quantum dot (QD) subjected to an external magnetic field B and affected by an impurity is studied. The impurity is located at the z-axis by a distance d from the plane of the dot. The evolution of the angular momentum L0 and the spin S0 of the ground state in accordance with B and d has been calculated, and the results are summarized and plotted in a (L0, S0) diagram. The spatial distribution of the electrons (the size and the geometric features) and the optical absorption have also been investigated. The (L0, S0) diagram indicates that L0 and S0 may jump when d and/or B vary. It was found that, due to the constraints arising from symmetry, each symmetric geometry is accessible only to a specific group of states having specific L0 and S0.