Electronic structure of many-electron square-well quantum dots with and without an attractive impurity: Spin-density-functional theory

The electronic structure of many-electron square-well quantum dots with and without an attractive impurity has been investigated within the spin-density-functional theory. We consider various sizes of quantum dots with the number of electrons varying from 2 to 20. We observe the emergence of localized Wigner-molecule-like behavior along with the wall-like feature in the charge density. However, unlike the parabolic quantum dots, we do not observe the analog of concentric rings. We also observe the typical broken symmetry configurations noted in earlier reports for quantum dots. The impurity induces the localized magnetic moment which, in many cases, generates the spin-polarized configurations with the antiferromagnetic coupling. An examination of the magnetic states indicates that the presence of impurity may change the ground state of quantum dot from magnetic to nonmagnetic and vice versa. We also observe that the localized charge at the center sharpens the walls.