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 $1350{\text{cm}}^{-1}$; 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.

• Received 5 April 2010

DOI:https://doi.org/10.1103/PhysRevB.82.241406