Absorption spectra of unequal width bilayer graphene nanoribbons in a spatially modulated electric field

The optical absorption spectra of unequal width bilayer graphene nanoribbons can be effectively tuned by a spatially modulated electric field. The absorption spectra exhibit many prominent peaks’ structure owing to the one-dimensional subbands. The number, spectral intensity, and frequency of the absorption peaks depend sensitively on the magnitude, period and phase of the modulated electric potential. The relative displacement between the top and bottom nanoribbons also has strong influence on the spectra. For unequal width bilayer graphene nanoribbons without the interlayer hoppings, there exists an optical selection rule originating from the spatial symmetry of the electron wave functions. Most importantly, such a selection rule can be disrupted by the presence of the interlayer atomic interactions or a spatially modulated electric field. These theoretical predictions can be validated by absorption spectroscopy experiments.