Zhao Yan, Zhang Shishu, Shi Yuping, Zhang Yanfeng, Saito Riichiro, Zhang Jin, Tong Lianming
Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, P.R. China.
Center for Nanochemistry, Beijing Science and Engineering Center for Nanocarbons, Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P.R. China.
ACS Nano. 2020 Aug 25;14(8):10527-10535. doi: 10.1021/acsnano.0c04467. Epub 2020 Aug 13.
We propose a technique of Raman spectroscopy to characterize the excitonic nature and to evaluate the relative contribution of the two kinds of electron/exciton-phonon interactions that are observed in two-dimensional transition-metal dichalcogenides (TMDCs). In the TMDCs, the electron/exciton-phonon interactions mainly originate from the deformation potential (DP) or the Fröhlich interaction (FI) which give the mutually different Raman tensors. Using a circularly polarized light, the relative proportion of the DP and the FI can be defined by the ratio of helicity-polarized intensity that is observed by MoS. By this analysis, we show that the excitonic FI interaction gradually increases with decreasing temperature, contributes equally to DP at ∼230 K, and dominates at lower temperatures. The excitonic effect in the Raman spectra is confirmed by modulating the dielectric environment for the exciton and by changing the laser power.
我们提出了一种拉曼光谱技术，用于表征二维过渡金属二硫属化物（TMDCs）中激子的性质，并评估所观察到的两种电子/激子 - 声子相互作用的相对贡献。在TMDCs中，电子/激子 - 声子相互作用主要源于形变势（DP）或弗罗利希相互作用（FI），它们给出相互不同的拉曼张量。使用圆偏振光，DP和FI的相对比例可以通过由MoS观察到的螺旋偏振强度的比率来定义。通过这种分析，我们表明激子FI相互作用随着温度降低而逐渐增加，在约230K时对DP的贡献相等，并且在较低温度下占主导地位。通过调节激子的介电环境和改变激光功率，证实了拉曼光谱中的激子效应。
