Ground State Transitions of Four-Electron Quantum Dots in Zero Magnetic Field

In this paper, we study four electrons confined in aparabolic quantum dot in the absence of magnetic field, by the exactdiagonalization method. The ground-state electronic structures and orbitaland spin angular momenta transitions as a function of the confinedstrength are investigated. We find that the confinement may causeaccidental degeneracies between levels with different low-lying states andthe inversion of the energy values. The present results are useful tounderstand the optical properties and internal electron-electroncorrelations of quantum dot materials.