Unusual Exciton–Phonon Interactions at van der Waals Engineered Interfaces

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• 作者：Colin M. ChowHongyi Yu ; Aaron M. Jones ; Jiaqiang Yan ; David G. Mandrus ; Takashi Taniguchi ; Kenji Watanabe ; Wang YaoXiaodong Xu
• 刊名：Nano Letters
• 出版年：2017
• 出版时间：February 8, 2017
• 年：2017
• 卷：17
• 期：2
• 页码：1194-1199
• 全文大小：429K
• ISSN：1530-6992

文摘

Raman scattering is a ubiquitous phenomenon in light–matter interactions, which reveals a material’s electronic, structural, and thermal properties. Controlling this process would enable new ways of studying and manipulating fundamental material properties. Here, we report a novel Raman scattering process at the interface between different van der Waals (vdW) materials as well as between a monolayer semiconductor and 3D crystalline substrates. We find that interfacing a WSe₂ monolayer with materials such as SiO₂, sapphire, and hexagonal boron nitride (hBN) enables Raman transitions with phonons that are either traditionally inactive or weak. This Raman scattering can be amplified by nearly 2 orders of magnitude when a foreign phonon mode is resonantly coupled to the A exciton in WSe₂ directly or via an A₁^′ optical phonon from WSe₂. We further showed that the interfacial Raman scattering is distinct between hBN-encapsulated and hBN-sandwiched WSe₂ sample geometries. This cross-platform electron–phonon coupling, as well as the sensitivity of 2D excitons to their phononic environments, will prove important in the understanding and engineering of optoelectronic devices based on vdW heterostructures.