Nondispersive Raman<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>D</mml:mi></mml:math>band activated by well-ordered interlayer interactions in rotationally stacked bilayer graphene

Abstract

Raman measurements on monolayer graphene folded back upon itself into skewed bilayer (i.e., with interlayer rotation) presents a mechanism for Raman scattering in $s{p}^{2}$ carbons in the $D$-band frequency range, but without disorder. Although the parent monolayer does not exhibit a $D$ band, the interior of the skewed bilayer produces a strong two-peak Raman feature near $1350\text{ }{\text{cm}}^{\ensuremath{-}1}$; one of these peaks is nondispersive, unlike all previously observed $D$-band features. Within a double-resonant model of Raman scattering, these features are consistent with a skewed bilayer coupling wherein one layer imposes a weak but well-ordered perturbation on the other. The discrete Fourier structure of the rotated interlayer interaction potential explains the unusual nondispersive peak.