Graphene/phosphorene bilayer: High electron speed, optical property and semiconductor-metal transition with electric field

We investigated the electric field dependent band structures and optical properties of graphene/phosphorene bilayer. Remarkably, the effective electron Fermi velocity in graphene/phosphorene was comparable to that of pure graphene monolayer. Moreover, this feature was not disrupted even in the presence of a finite external electric field. The electronic band structure changed from a semiconductor to a metallic state with an external electric field strength of 0.5 V/Å. In addition, the electric field enhanced the structural stability of a bilayer system because the binding energy was increased approximately 20-30% as compared with that at zero electric field. We found that the optical anisotropy regarding the electric polarization along armchair and zigzag directions disappeared, but the anisotropic optical properties still survived regarding the electric polarization for in-plane and perpendicular directions. The small effective mass, high speed of electrons, and optical property in graphene/phosphorene bilayer may provide a promising way for graphene based device applications.