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Abstract: Through the tight-binding model, the effect of electric field on electronic and optical properties of a zigzag (an armchair) H-terminated nanographite ribbon is studied. The effective electric field shifts the Fermi level (E F), modifies the energy dispersions, alters the subband spacing, produces the new edge state, changes the band gap, and causes the semiconductor–metal transitions. First, in the metallic zigzag ribbon, the degeneracy of flat bands at E F is lifted by the electric field. Meanwhile, an energy band gap E g, depending on the ribbon width and the field strength, is induced. And while the field strength increases, the semiconductor–metal transition occurs in both the semiconducting armchair and the zigzag ribbons. Then, the effect of electric field on band structures is completely reflected in the features of density of states—the shift of peak position, the change of peak height and the alternation of band gap. Most importantly, the effective electric field has great influence on the low-energy absorption spectra. It can change frequency of the first peak, alter the peak height, and even produce the new peaks. [Copyright &y& Elsevier]

Abstract: The transport properties of carbon nanoscrolls in a uniform electric field are investigated by using the Landauer–Buttiker formula. The energy dispersions depend sensitively on the geometry and the field strength. The bandgaps may become zero and exhibit the semiconductor-metal transitions. Variations in the electronic structures with the geometry or the field strength are reflected in the conductance. The conductance exhibits a stepwise behavior, caused by the discrete number of quantized channels contributing to transport. The shoulders of the conductance are stretched out as temperature rises. [Copyright &y& Elsevier]

Abstract: The tight-binding model is employed to study magnetoelectronic structures of the AB-stacked graphite. A specifically full band calculation on overall energy region is presented to compare with SWMcC method, which only concerns the magnetoelectronic structures along the HKH-axis. It is found that magnetoband structures, strongly depending on the perpendicular magnetic field (B) and the interlayer interactions, exhibit 0D, 1D and 2D characteristics at the strong magnetic field. The physical origin of 0D, 1D and 2D Landau levels is intensely discussed to show its speciality for graphite. Pronounced structures, including sharp peaks, square-root peaks, and logarithmic divergences, can be clearly found in the density of states (DOS). And the energy dispersions and DOS are specially sensitive to the magnitude of B: the lower the magnetic field is, the more Landau levels exist nearby Fermi energy (E F). Meanwhile, the interlayer interactions significantly affect the state energies and the DOS features, e.g., peak position and peak shape. DOS in the form of sharp peak (square-root peaks) below (above) E F is expected to play an important role in such physical properties as absorption spectra. [Copyright &y& Elsevier]