SIM-RUC
Surface & Interface Modeling
for Emerging Nanomaterials and Devices

moiré Phonons in Twisted Bilayer MoS2

Miao-Ling Lin,†,‡,⊥ Qing-Hai Tan,†,‡,⊥ Jiang-Bin Wu,† Xiao-Shuang Chen,¶ Jin-Huan Wang,§ Yu-Hao Pan,∥ Xin Zhang,† Xin Cong,†,‡ Jun Zhang,†,‡ Wei Ji,∥ Ping-An Hu,¶ Kai-Hui Liu,§ and Ping-Heng Tan*,†,‡

†State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 6 100083, China
‡CAS Center of Excellence in Topological Quantum Computation and College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Beijing 101408, China
¶School of Materials Science and Engineering, MOE Key Laboratory of Micro-Systems and Micro-Structures Manufacturing, Harbin Institute of Technology, Harbin 150080, P. R. China
§State Key Laboratory of Mesoscopic Physics, School of Physics and Collaborative Innovation Center Quantum Matter, Peking University, Beijing 100871, China
∥Department of Physics, Renmin University of China, Beijing 100872, China

DOI:10.1021/acsnano.8b05006     Publication Date: 


Abstract:

The material choice, layer thickness, and twist angle widely enrich the family of van der Waals 16 heterostructures (vdWHs), providing multiple degrees of freedom to engineer their optical and electronic properties. The 17 moirépatterns in vdWHs create a periodic potential for electrons and excitons to yield many interesting phenomena, such 18 as Hofstadter butterfly spectrum and moiré excitons. Here, in the as-grown/transferred twisted bilayer MoS2 (tBLMs), 19 one of the simplest prototype of vdWHs, we show the periodic potentials of moirépatterns can also modify the properties 20 of phonons of its monolayer MoS2 constituent to generate Raman modes related to moiréphonons. These Raman modes 21 correspond to zone-center phonons in tBLMs, which are folded from the off-center phonons in monolayer MoS2. 22 However, the folded phonons related to crystallographic superlattices are not observed in the Raman spectra. By varying 23 the twist angle, the moiré phonons of tBLM can be used to map the phonon dispersions of the monolayer constituent. 24 The lattice dynamics of the moiré phonons are modulated by the patterned interlayer coupling resulting from periodic 25 potential of moirépatterns, as confirmed by density functional theory calculations. The Raman intensity related to moiré 26 phonons in all tBLMs are strongly enhanced when the excitation energy approaches the C exciton energy. This study can 27 be extended to investigate Raman spectra in various vdWHs to deeply understand their Raman spectra, moiré phonons, 28 lattice dynamics, excitonic effects, and interlayer coupling.


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View: ACS NANO  , ASAP (2018)    

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