Fig. 4: Phenomenological model of phonon frequency combs.
From: Spontaneously formed phonon frequency combs in van der Waals solid CrGeTe3 and CrSiTe3
a An illustration of the detailed oscillation pattern of the \({A}_{{{{\rm{g}}}}}^{5}\) mode on the Ge2Te6 cluster. The arrows are not proportional to the actual atomic oscillation amplitude. b Schematics of the Raman scattering process, anharmonic potential, and associated energy levels. c Calculated frequency comb Raman spectra from Eq. (6) with different α0 values. d, e Fitting of the frequency comb with the Fourier transform of Eq. (6) for the 633 nm and 532 nm data, respectively. f Simulation of the atomic movement in the real space for the frequency comb in (d), compared with inverse Fourier transform from the Lorentzian part of the fit in Fig. 2a. The insets highlight the first revival of the oscillation.
