| Summary: | 博士 === 國立成功大學 === 物理學系碩博士班 === 94 === In this thesis, coulomb excitations and deexcitations of a monolayer graphite are
studied within random-phase approximation. A monolayer graphite exhibits rich low-frequency excitation spectra, mainly owing to the zero-gap characteristic. There exist interband e-h excitations, intraband e-h excitations, and plasmon. The latter two are purely caused by temperature. Interband e-h excitations are the only deexcitations mechanism for Fermi-momentum state. As to other states, three kinds of excitations are responsible for decay rates. The formulas of coulomb excitations for multilayered graphite are derived within random-phase approximation. Coulomb excitations of two typical bilayer graphites with different stacking sequences are studied. They are strongly affected by the stacking sequence, the interlayer coulomb interaction, and the momentum transfer. However, they hardly depend on the direction of momentum transfer and the temperature. The electronic structure of a monolayer graphite under the spatially modulated field is studied by tight-binding model. Electronic properties strongly depend on the strength, the direction, and the period of modulated fields. Such fields could lead
to the drastic changes in state degeneracy, energy dispersions, band spacings, wave functions, and band-edge states. Hence, density of states exhibits several special structures.
|
|---|
