Probing interlayer interaction via chiral phonons in layered honeycomb materials

van der Waals (vdW) interaction plays a significant role in controlling the physical properties of layered materials. Typically, the vdW interlayer interaction can be calculated by density functional theory or experimentally characterized by quantum capacitance measurement. Here, we report the probing of the interlayer interaction in layered honeycomb materials via chiral phonons. Through helicity resolved Raman measurements, we observed a reduced chirality of the Raman $G$ mode with increasing layer numbers. We introduced interlayer coupling terms into the traditional Raman $G$ mode tensor to simulate the reduced phonon chirality in Raman spectra. Our Raman tensor calculation results agree with the experiments well, suggesting that the interlayer interaction can significantly influence the lattice vibration. Our demonstration provides a perspective for characterizing the interlayer interactions in vdW layered materials with honeycomb lattice structure.