Quantum dots with interacting electrons: Energy spectra and magnetization

The energy spectra and magnetization of a two-electron, square quantum dot is investigated theoretically by numerical diagonalization of the many-part icle Hamiltonian of the system. The electron-electron interaction is found to lift many degeneracies between spin-singlet and spin-triplet states of n oninteracting electrons and induce many energy level crossings and anticros sings. It is found that the interaction increases the magnitude of magnetiz ation in the low magnetic field region and induce magnetization oscillation s in the moderate and strong held regions. The effect of the interaction on the magnetization is also studied when a repulsive delta-function impurity is present at the center of the quantum dot. The impurity is found to weak en the many-particle effect on the magnetization iu the low magnetic held r egion. It is also found that the interaction tends to screen the impurity a nd weaken the effect of the impurity in the quantum dot. (C) 1998 Elsevier Science B.V. All rights reserved.