Slater-Koster parametrization for the phonons of monolayer MoX₂(X = S, Se or Te)

With the help of the Slater-Koster parametrization, we construct simplified force constant (FC) models to describe the phonons of several two-dimensional (2D) transition metal dichalcogenides (TMDs) (MoX₂, X = S, Se or Te) by only considering the FCs to fourth-nearest-neighbor interactions. By fitting the phonon dispersions derived from first-principles calculations, we find these models can well describe the symmetry characters and semimetal states of MoX₂'s phonons. Combining the basis of the FC model and the theory of tensor representation, we derive the origin of the irreducible representations at the high symmetry points Γ,KandM. Moreover, by using the compatibility relation between high symmetry points and high symmetry lines, we find the semimetal states of MoX₂are protected by vertical and horizontal mirrors. Our work provides an effective tool to further study the phonons of 2D TMDs.