Physical origin of Davydov splitting and resonant Raman spectroscopy of Davydov components in multilayer MoTe 2

作者：Qingjun Song, Qinghai Tan, Xin Zhang, Jiangbin Wu, Bowen Sheng, Yi Wan, X. Q. Wang, Lun Dai, Ping‐Heng Tan · 发表于：Physical review. B./Physical review. B · 年份：2016 · DOI：10.1103/physrevb.93.115409 · 被引用次数：113 · 研究领域：2D Materials and Applications、Perovskite Materials and Applications、Topological Materials and Phenomena

We systematically study the high-resolution and polarized Raman spectra of multilayer (ML) ${\mathrm{MoTe}}_{2}$. The layer-breathing (LB) and shear (C) modes are observed in the ultralow-frequency region, which are used to quantitatively evaluate the interlayer coupling in ML ${\mathrm{MoTe}}_{2}$ based on the linear chain model, in which only the nearest interlayer coupling is considered. The Raman spectra on three different substrates verify the negligible substrate effect on the phonon frequencies of ML ${\mathrm{MoTe}}_{2}$. Ten excitation energies are used to measure the high-frequency modes of $N$-layer ${\mathrm{MoTe}}_{2}$ ($N\mathrm{L} {\mathrm{MoTe}}_{2}$; $N$ is an integer). Under the resonant excitation condition, we observe $N$--dependent Davydov components in ML ${\mathrm{MoTe}}_{2}$, originating from the Raman-active ${A}_{1}^{\ensuremath{'}}({A}_{1g}^{2})$ modes at \ensuremath{\sim}$172\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$. More than two Davydov components are observed in $N\mathrm{L} {\mathrm{MoTe}}_{2}$ for $N>4$ by Raman spectroscopy. The $N$-dependent Davydov components are further investigated based on the symmetry analysis. A van der Waals model only considering the nearest interlayer coupling has been proposed to well understand the Davydov splitting of high-frequency ${A}_{1}^{\ensuremath{'}}({A}_{1g}^{2})$ modes. The different resonant profiles for the two Davydov components in 3L ${\mathrm{MoTe}}_{2}$ indicate that...