J. H. Ho

Electronic properties of AA- and ABC-stacked few-layer graphites

The low-energy electronic properties of a few graphite layers with AA and ABC stacking under application of the electric field (F), perpendicular to the layers, are explored through the tight-binding model. They strongly depend on the interlayer interactions, the stacking sequences, the layer numbers, and the field strength. In the absence or presence of F, the AA-stacked N-layer graphites (N ¼ 3 and 4) exhibit the linear bands near the Fermi energy. The interlayer interactions and electric field chiefly shift the Fermi momenta and the state energies. The ABC-stacked N-layer graphites are characterized by the complicated low-energy bands due to the stacking effect, on which F has a great influence—the change of the state energies and the subband spacing, the opening of a band gap, the production of the oscillating bands, and the increase of the band-edge states. As a result, the two kinds of special structure, whose positions and heights are modulated by F, are found in the density of states (DOS) in contrast to the featureless DOS of the AA systems. The comparison with the AB-stacked few-layer graphites is also made.

Semimetallic graphene in a modulated electric potential

The

Magnetoelectronic Properties of a Single-Layer Graphite

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Electronic and optical properties of a nanographite ribbon in an electric field

-electronic structure of graphene in the presence of a modulated electric potential is investigated by the tight-binding model. The low-energy electronic properties are strongly affected by the modulation period and potential strength. Such a potential could modify the energy dispersions, destroy state degeneracy, and induce band-edge states. One striking feature happens close to the Fermi level that the light-cone structure is replaced with two distinct kinds of valley structures with highly anisotropic energy dispersion. Both valleys are highlighted by the existence of the quasi-one-dimensional electronic states, whereas they are distinguished one from the other by the different directions of restricted motion of charge carriers. It should be noted that a modulated electric potential could make semiconducting graphene semimetallic, and that the onset period of such a transition relies on the field strength. The finite density of states (DOS) at the Fermi level means that there are free carriers, and, at the same time, the low DOS spectrum exhibits many prominent peaks, mainly owing to the band-edge states.

Landau levels in graphene

The magnetoelectronic structure of a single-layer graphite is mainly determined by the strength, the period, and the direction of the modulated magnetic field. Such field could induce the destruction of state degeneracy, the drastic change of energy dispersion, the increment of band-edge states, and the alternation of band width. Most of energy bands become nondegenerate, and the flat bands are replaced by the parabolic bands. Density of states exhibits the linear energy dependence, the square-root divergences, the logarithmic divergences, the discontinuous structures, and the delta-function-like divergences. These special structures directly reflect rich energy spectra.