Numerical studies of transport properties through artificial atoms and molecules

Transport properties are studied numerically through a quantum dot in which one-electron level spacings are comparable with the Coulomb interaction energy. Many-body ground state and excited states are obtained by the exact diagonalization method. An atomic-like shell structure of energy levels is reflected in peak positions of the Coulomb oscillation, whereas almost degenerate levels in a shell cause anomalous temperature dependence of some peak heights. When such artificial atoms are coupled like a molecule, the electronic correlation makes the Heitler-London wavefunction in which electrons are localized to be apart from each other. This correlation effect influences the peak heights of the Coulomb oscillation through the artificial molecule.