| Summary: | 博士 === 國立成功大學 === 物理學系碩博士班 === 101 === The single- and many-particle Coulomb excitation spectra modulated by a uniform perpendicular electric field in AA- and AB-stacked few-layer graphenes are numerically and analytically investigated within the tight-binding model and the random-phase approximation. In Bernal bilayer graphene, the field-induced oscillatory parabolic
bands possess saddle points and local extrema, which, respectively, lead to logarithmically divergent peaks and discontinuous steps in the bare response functions. Such special structures are associated with the plasmon peaks in the screened loss spectra. A few prominent interband plasmons are thus generated. For simple hexagonal bilayer
graphene, the electronic excitations are related to field-dependent Fermi-momentum states. The presence of such a field destroys the uniform probability distribution of the four sublattices. This drives a symmetry breaking between the intralayer and interlayer polarization intensities in the intrapair band excitations. A field-induced acoustic plasmon thus emerges in addition to the field-tunable intrinsic acoustic and optical plasmons. At long wavelengths, the three modes show different dispersions and field dependence. The frequencies calculated from the vanishing real-part determinant of the dielectric function matrix are consistent with those obtained from the numerical loss functions. The definite physical mechanism of the electrically inducible and tunable mode is also present in other AA-stacked few-layer graphenes. The field is further capable of manipulating the energy, intensity, and number of the optical plasmon modes in AA-stacked trilayer and tetralayer graphenes. The predicted results could be examined by inelastic light scattering spectroscopy and electron-energy-loss spectroscopy. These analytical derivations are useful in understanding other
many-body effects.
|
|---|
