Clarifying intralayer and interlayer electron-phonon interaction of bilayer graphene with isotope-labelled Raman spectroscopy

The interaction between electrons and phonons in two-dimensional van der Waals materials governs their crucial physical properties. Here, we study the intra- and interlayer electron-phonon (el-ph) interaction of bilayer graphene (BLG) using isotope-labeled Raman spectroscopy. Results show that the G, R and R’ peak of BLG with different twisted angles all originate from the intralayer el-ph interaction, in which the resonance of G and R peaks are both related with the intralayer electronic transition connecting the van Hove singularities in the density of electronic states, while the resonance of R’ peak are driven by the double resonance condition. And three peaks with different dispersions appear around 3170 cm−1 in BLG with certain twist angles, which are assigned as the 2G, G + R’ and 2R’ peaks that all from the interlayer el-ph interaction. Our findings facilitate a better understanding of el-ph interaction in the BLG system.