Two-dimensional transition metal dichalcogenides（TMDs） have attracted extensive attention due to their many novel properties.The atoms within each layer in two-dimensional TMDs are joined together by covalent bonds,...Two-dimensional transition metal dichalcogenides（TMDs） have attracted extensive attention due to their many novel properties.The atoms within each layer in two-dimensional TMDs are joined together by covalent bonds,while van der Waals interactions combine the layers together.This makes its lattice dynamics layer-number dependent.The evolutions of ultralow frequency（〈 50 cm^（-1）） modes,such as shear and layer-breathing modes have been well-established.Here,we review the layer-number dependent high-frequency（〉 50 cm^（-1）） vibration modes in few-layer TMDs and demonstrate how the interlayer coupling leads to the splitting of high-frequency vibration modes,known as Davydov splitting.Such Davydov splitting can be well described by a van der Waals model,which directly links the splitting with the interlayer coupling.Our review expands the understanding on the effect of interlayer coupling on the high-frequency vibration modes in TMDs and other two-dimensional materials.展开更多
基金Project supported by the National Basic Research Program of China(No.2016YFA0301200)the National Natural Science Foundation of China(Nos.11225421,11474277,11434010,61474067,11604326,11574305 and 51527901)the National Young 1000 Talent Plan of China
文摘Two-dimensional transition metal dichalcogenides（TMDs） have attracted extensive attention due to their many novel properties.The atoms within each layer in two-dimensional TMDs are joined together by covalent bonds,while van der Waals interactions combine the layers together.This makes its lattice dynamics layer-number dependent.The evolutions of ultralow frequency（〈 50 cm^（-1）） modes,such as shear and layer-breathing modes have been well-established.Here,we review the layer-number dependent high-frequency（〉 50 cm^（-1）） vibration modes in few-layer TMDs and demonstrate how the interlayer coupling leads to the splitting of high-frequency vibration modes,known as Davydov splitting.Such Davydov splitting can be well described by a van der Waals model,which directly links the splitting with the interlayer coupling.Our review expands the understanding on the effect of interlayer coupling on the high-frequency vibration modes in TMDs and other two-dimensional materials.
