Raman tensor of graphite: Symmetry of G, D and D′ phonons

Since the first record of Raman spectra of graphite in 1970, the physical origin behind its Raman characteristic peaks (i.e., G, D and D' peaks) has been a focus of controversy. At present, it is generally believed that G peak corresponds to Raman active E 2g2 mode, while D and D' peaks are defect-induced ones. However, unequivocal experimental evidence for the phonon symmetries for these graphite Raman peaks is almost still in blank. Here, we clarify these important aspects using an angle resolved polarized Raman spectroscopy. It is found that the experimental Raman intensity of D and D' peaks shows a similar polarized angle dependence as that of G peak. Combined with Raman tensor analysis and double-resonant mechanism, the phonon symmetry of D' and D peak is further understood. Our work provides reliable experimental evidence and reasonable explanation for better understanding the phonon symmetry of graphite.