Electric-field-induced plasmon in AA-stacked bilayer graphene

• The analytical derivations are performed by the tight-binding model.
• An electric field drives the non-uniformity of the charge distribution.
• A symmetry breaking between the intralayer and interlayer polarizations is illustrated.
• An extra plasmon emerges besides two intrinsic modes in AA-stacked bilayer graphene.
• The mechanism of a field-induced mode is present in AA-stacked few-layer graphenes.

The collective excitations in AA-stacked bilayer graphene for a perpendicular electric field are investigated analytically within the tight-binding model and the random-phase approximation. Such a field destroys the uniform probability distribution of the four sublattices. This drives a symmetry breaking between the intralayer and interlayer polarization intensities from the intrapair band excitations. A field-induced acoustic plasmon thus emerges in addition to the strongly field-tunable intrinsic acoustic and optical plasmons. At long wavelengths, the three modes show different dispersions and field dependence. The definite physical mechanism of the electrically inducible and tunable mode can be expected to also be present in other AA-stacked few-layer graphenes.