Kikuo Harigaya

Spin- and charge-polarized states in nanographene ribbons with zigzag edges

Effects of the nearest-neighbor Coulomb interaction on nanographene ribbons with zigzag edges are investigated using the extended Hubbard model within the unrestricted Hartree-Fock approximation. The nearest Coulomb interaction stabilizes an electronic state with the opposite electric charges separated and localized along both edges, resulting in a finite electric dipole moment pointing from one edge to the other. This charge-polarized state competes with the peculiar spin-polarized state caused by the on-site Coulomb interaction and is stabilized by an external electric field.

OPTICAL-ABSORPTION SPECTRA IN FULLERENES C60 AND C70 : EFFECTS OF COULOMB INTERACTIONS, LATTICE FLUCTUATIONS, AND ANISOTROPY

Effects of Coulomb interactions and lattice fluctuations in the optical-absorption spectra of

Anisotropic Magnetoresistance Effects in Fe, Co, Ni, Fe4N, and Half-Metallic Ferromagnet: A Systematic Analysis

{\mathrm{C}}_{60}

The mechanism of magnetism in stacked nanographite: theoretical study

and

Magnetic Structure of Nano-Graphite Mobius Ribbon

{\mathrm{C}}_{70}

Lattice and Electronic Structuresof Undoped and Doped C60 Moleculesby the Extended Su-Schrieffer-Heeger Model

are theoretically investigated by using a tight-binding model with long-range Coulomb interaction and bond disorder. Anisotropy effects in

Lattice distortion and energy-level structures in doped C70 by the extended Su—Schrieffer—Heeger model

{\mathrm{C}}_{70}

Quantum lattice fluctuations and luminescence in C60.

are also considered. Optical spectra are calculated by using the Hartree-Fock approximation followed by the configuration interaction method. The main conclusions are as follows. (1) The broad peaks at excitation energies, 3.7, 4.7, and 5.7 eV, observed in experiments of

METAL-INSULATOR TRANSITION IN C60 POLYMERS

{\mathrm{C}}_{60}

Dispersion of the Third-Order Nonlinear Optical Susceptibility in C60 Calculated with a Tight-Binding Model

molecules in a solution, are reasonably described by the present theory. Peak positions and relative oscillator strengths are in overall agreement with the experiments. The broadening of peaks by lattice fluctuations is well simulated by the bond disorder model. (2) The optical gap of