Combined Effect of Stacking and Magnetic Field on Plasmon Excitations in Bilayer Graphene

Abstract: The electronic excitations of bilayer graphene (BLG) under a magnetic field are investigated with the use of the Peierls tight-binding model in conjunction with random-phase approximation (RPA). The interlayer atomic interactions, interlayer Coulomb interactions, and magnetic field effects are simultaneously included in the dielectric-function matrix. That enables us to derive the magneto-Coulomb-excitation spectrum of different stacking structures. The two typical arrangements of BLGs, AB and AA, are considered in this article. AB-BLG exhibits many discrete energy-loss peaks, which correspond to the quantization of electron energies. On the other hand, the AA-BLG spectra possess a unique and pronounced peak at low frequency. This peak represents the collective excitation of the entire low-frequency Landau states. The dependence of the energy-loss peaks on the momentum transfer and the magnetic field strength is presented. Accordingly, two kinds of plasmon modes produced by the layer stacking are clearly distinguished.