Impurity effect on low-lying spectra in a two-electron quantum dot with parabolic confinement

Using an exact numerical diagonalization scheme, we calculated the low-lying spectra of a two-electron quantum dot with a confined parabolic potential in the presence of a Coulomb impurity at the center under a perpendicular homogeneous magnetic field. Numerical results show that for the low spectra of on-center acceptor impurity, the orbital angular momentum L-transition and/or spin angular momentum S-transition takes place in the ground state, which is qualitatively the same as the case without impurity, while for the low-lying spectra of on-center donor impurity, there are no ground state transitions and the energy spectra are completely different