Influence of the electric field on the optical properties of bilayer graphene nanoribbons*

Increasing attention has been paid to multilayer graphene, especially to bilayer graphene nanoribbons (BLGNRs)[1]. The interlayer interactions in BLGNRs result in a deformation of the electronic band structure with a change in the slope of the subbands. Recent studies show that the bandgap of BLG is widely tunable by external electric fields (EF) [2,3]. Here, the optical properties of BLGNRs under effects of EF are investigated by using a tight-binding model and the gradient approximation. The EF can induce the subband (anti)crossing, change the subband spacing, cause the oscillating bands, and distort the band-edge states as well. Our results demonstrate that the optical absorption spectra exhibit rich prominent peaks that mainly stem from the subbands. In addition, the number, spectral intensity, and energy of the absorption peaks are strongly dependent on the interlayer atomic interactions and the ribbon width. The dependence of the optical excitations on both the magnitude and direction of the EF is studied as well. This study could be validated by optical spectroscopy measurements. These results provide a view of the possibilities for applying future optoelectronic applications base on BLGNRs.