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Abstract
Graphene and other two-dimensional crystals can be combined to form various hybrids
and heterostructures, creating materials on demand with properties determined by the
interlayer interaction. This is the case even for a single material, where multilayer
stacks with different relative orientation have different optical and electronic properties.
Probing and understanding the interface coupling is thus of primary importance for
fundamental science and applications. Here we study twisted multilayer graphene flakes
with multi-wavelength Raman spectroscopy. We find a significant intensity enhancement
of the interlayer coupling modes (C peaks) due to resonance with new optically allowed
electronic transitions, determined by the relative orientation of the layers. The
interlayer coupling results in a Davydov splitting of the C peak in systems consisting
of two equivalent graphene multilayers. This allows us to directly quantify the interlayer
interaction, which is much smaller compared with Bernal-stacked interfaces. This paves
the way to the use of Raman spectroscopy to uncover the interface coupling of two-dimensional
hybrids and heterostructures.