The coupling between the interlayer magnetic order and Davydov splitting modes in few-layer CrI3

The magnetic order in 2D material CrI3 has a significant impact on the Raman polarization selection rules of phonons, as evidenced by magneto-optical Raman spectroscopy. In a monolayer, the forbidden Raman scattering of A(1g) mode can be detected in the XY channel at low temperatures. However, in the bilayer, the A(g) mode splits into two modes, and the selection rules of the splitting modes are determined by the magnetic order and symmetry. In contrast, the inversion symmetry of the spin structure is maintained in both antiferromagnetic (AFM) and ferromagnetic (FM) states in the trilayer (3L) CrI3, and the evolution of its Raman scattering with magnetic field is not yet clear. In this work, we use magneto-optical polarized Raman spectroscopy and reflective magnetic circular dichroism to investigate the Davydov splitting of the A(g) phonon mode and its coupling to layered magnetism in 2-5L CrI3. Our results show that the Raman scattering of the A(g) mode is strongly coupled to the layered magnetic order, indicating strong spin-phonon coupling in CrI3. Our study might shed light on the research on interaction between magnetic and vibrational properties of 2D magnetic materials and provide important implications for developing novel 2D spintronic devices.