Absorption spectra of asymmetric bilayer graphene nanoribbons

•We study the absorption spectra of asymmetric bilayer graphene nanoribbons.•The absorption peaks depend sensitively on the interlayer interactions, geometry, and electric field.•The interlayer interactions or electric field disrupt the wave function spatial symmetry and the optical selection rule.

The low-frequency optical absorption properties of asymmetric bilayer graphene nanoribbons in an external electric field are investigated by using the gradient approximation. This study shows that the optical absorption spectra exhibit rich prominent peaks structure mainly owing to the one-dimensional subbands. For asymmetric bilayer graphene nanoribbons without the interlayer atomic interactions, there exists an optical selection rule which is caused by the spatial symmetry of the wave functions. Furthermore, such selection rule does not exist with the presence of the interlayer hoppings or an external electric field. In addition, the number, spectral intensity, and energy of the absorption peaks are strongly dependent on the interlayer atomic interactions, the magnitude and direction of the electric field, the relative displacement between the nanoribbons, and the ribbon width. The presented results can be validated by absorption spectroscopy measurements.

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