Current-spin density-functional theory of the electronic and magnetic properties of quantum dots and quantum rings

A systematic investigation of the electronic states and magnetism in quantum dots and quantum rings within current-spin density-functional theory (CSDFT) has been performed. CSDFT allows for studying the combined effects of confinement, Coulomb interaction, spin polarization, and magnetic field for a realistic dot or ring system. The dot and ring systems are considered to be three dimensional and the screening due to the gate electrodes is included. The chemical potential, addition energy, and spontaneous magnetization for a quantum dot and a quantum ring in zero magnetic field have been calculated as a function of electron number. A number of spin-polarized ground states in both the quantum dot and the quantum ring, which generally obey Hund’s rule, are found. The chemical potential, spin magnetization, orbital angular momentum, and persistent current in the quantum systems under a magnetic field have also been calculated. With increasing magnetic field, a rich variety of transitions between the ground states with different orbital angular momentum and spin configuration are predicted. The calculated addition energy spectrum of the quantum dot reproduces the observed spectrum very well, especially, the charging energy, exchange energy, and shell structure. The features in the calculated chemical potential versus magnetic-field spectra of the quantum dot, which reflect the many-electron state transitions, agree well with those observed in the experiments, indicating that CSDFT is a useful tool for studying the correlated electrons in quantum dots and quantum rings.