Resonance Raman spectroscopy in twisted bilayer graphene

• Published in: Solid state communications 2013-12, Vol.175-176, p.13-17
• Main Authors: Righi, A., Venezuela, P., Chacham, H., Costa, S.D., Fantini, C., Ruoff, R.S., Colombo, L., Bacsa, W.S., Pimenta, M.A.
• Format: Article
• Language: English
• Subjects: A. Twisted bilayer graphene; D. Umklapp double-resonance; E. Resonance Raman scattering
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/j.ssc.2013.05.015

In this work we study the Raman spectra of twisted bilayer graphene samples, with different twisting angles, by changing the incident laser energy between 2.54 and 4.14eV. The spectra exhibit a number of extra peaks, classified in different families, each one associated with bilayer graphenes with different twisting rotational angles. We theoretically analyze the laser energy dependence of these extra peaks considering a set of discrete wavevectors within the interior of the Brillouin zone of graphene, which activate special double-resonance Raman processes. Our result show a nice qualitative agreement between the experimental and simulated spectra, demonstrating that these extra peaks are indeed ascribed to an umklapp double-resonance process in graphene systems. •We studied the resonance Raman spectra of twisted bilayer graphene.•The spectra exhibit extra peaks associated with different twisting angles.•We have measured and simulated the laser energy dependence of the extra peaks.•We observed a nice agreement between the experimental and simulated spectra.•Our results are explained by an umklapp double-resonance process in graphene.