Davydov Splitting and Excitonic Resonance Effects in Raman Spectra of Few-Layer MoSe2

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• 作者：Kangwon Kim ; Jae-Ung Lee ; Dahyun Nam ; Hyeonsik Cheong
• 刊名：ACS Nano
• 出版年：2016
• 出版时间：August 23, 2016
• 年：2016
• 卷：10
• 期：8
• 页码：8113-8120
• 全文大小：3138K
• 年卷期：0
• ISSN：1936-086X

文摘

Raman spectra of few-layer MoSe₂ were measured with eight excitation energies. New peaks that appear only near resonance with various exciton states are analyzed, and the modes are assigned. The resonance profiles of the Raman peaks reflect the joint density of states for optical transitions, but the symmetry of the exciton wave functions leads to selective enhancement of the A_1g mode at the A exciton energy and the shear mode at the C exciton energy. We also find Davydov splitting of intralayer A_1g, E_1g, and A_2u modes due to interlayer interaction for some excitation energies near resonances. Furthermore, by fitting the spectral positions of interlayer shear and breathing modes and Davydov splitting of intralayer modes to a linear chain model, we extract the strength of the interlayer interaction. We find that the second-nearest-neighbor interlayer interaction amounts to about 30% of the nearest-neighbor interaction for both in-plane and out-of-plane vibrations.