Layer-number dependent high-frequency vibration modes in few-layer transition metal dichalcogenides induced by interlayer couplings 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), and the National Young 1000 Talent Plan of China

• Published in: Journal of semiconductors 2017-03, Vol.38 (3)
• Main Authors: Tan, Qing-Hai, Zhang, Xin, Luo, Xiang-Dong, Zhang, Jun, Tan, Ping-Heng
• Format: Article
• Language: English
• Subjects: Davydov splitting; interlayer coupling; Raman spectroscopy; transition metal dichalcogenides; van der Waals model
• ISSN: 1674-4926
• DOI: 10.1088/1674-4926/38/3/031006

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.