Fig. 6: Determining the energy barrier of the structural phase transition in TLG.

a 2D color plot of Raman shifts of G bands as a function of applied laser power. b The change in Raman shifts of the G bands (left axis) and the determined lattice temperature (right axis) of TLG. The data are from sample #2. The error bars are determined by the uncertainty of the coefficient γ (0.011 cm⁻¹ K⁻¹ ~ 0.016 cm⁻¹ K⁻¹). The red solid curve is the lattice temperature of TLG calculated by the heat diffusion equation. The horizontal black dashed line marks the threshold temperature T_ts ~ 430 K for the structural transition in TLG under 10 mW laser irradiation. c DFT calculations of the minimum energy transition path of TLG from ABC stacking to ABA stacking using the NEB method. The red squares represent the calculation performed by means of the SCAN + rVV10 functional, while the blue dots represent the calculation performed by means of the LDA functional. The dashed curves are visual guides obtained by Gaussian fitting. The schematics at the bottom illustrate three different stacking configurations of TLG and the process of ABC-to-ABA structural phase transition