Visualizing the Anomalous Charge Density Wave States in Graphene/NbSe2 Heterostructures,Advanced Materials

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Visualizing the Anomalous Charge Density Wave States in Graphene/NbSe2 Heterostructures
Advanced Materials ( IF 27.4 ) Pub Date : 2020-10-01 , DOI: 10.1002/adma.202003746
Yu Chen _{1,

2} , Lishu Wu ₂ , Hai Xu _{3,

4,

5} , Chunxiao Cong _{6,

7} , Si Li ₈ , Shun Feng ₂ , Hongbo Zhang ₂ , Chenji Zou ₂ , Jingzhi Shang _{1,

2} , Shengyuan A. Yang ₈ , Kian Ping Loh ₃ , Wei Huang _{1,

9} , Ting Yu ₂

Affiliation

Shaanxi Institute of Flexible Electronics (SIFE) Northwestern Polytechnical University (NPU) Xi'an 710129 China
Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore
Department of Chemistry National University of Singapore Singapore 117543 Singapore
Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Science Changchun 130033 China
Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100040 China
State Key Laboratory of ASIC and System School of Information Science and Technology Fudan University Shanghai 200433 China
Academy for Engineering and Technology Fudan University Shanghai 200433 China
Research Laboratory for Quantum Materials Singapore University of Technology and Design Singapore 487372 Singapore
Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM) Nanjing Tech University (NanjingTech) Nanjing 211800 China

Metallic layered transition metal dichalcogenides (TMDs) host collective many‐body interactions, including the competing superconducting and charge density wave (CDW) states. Graphene is widely employed as a heteroepitaxial substrate for the growth of TMD layers and as an ohmic contact, where the graphene/TMD heterostructure is naturally formed. The presence of graphene can unpredictably influence the CDW order in 2D CDW conductors. This work reports the CDW transitions of 2H‐NbSe₂ layers in graphene/NbSe₂ heterostructures. The evolution of Raman spectra demonstrates that the CDW phase transition temperatures (T_CDW) of NbSe₂ are dramatically decreased when capped by graphene. The induced anomalous short‐range CDW state is confirmed by scanning tunneling microscopy measurements. The findings propose a new criterion to determine the T_CDW through monitoring the line shape of the A_1g mode. Meanwhile, the 2D band is also discovered as an indicator to observe the CDW transitions. First‐principles calculations imply that interfacial electron doping suppresses the CDW states by impeding the lattice distortion of 2H‐NbSe₂. The extraordinary random CDW lattice suggests deep insight into the formation mechanism of many collective electronic states and possesses great potential in modulating multifunctional devices.

中文翻译：

可视化石墨烯/ NbSe2异质结构中的异常电荷密度波状态

金属层状过渡金属二硫化碳（TMD）具有集体多体相互作用，包括竞争的超导和电荷密度波（CDW）状态。石墨烯被广泛用作异质外延衬底，用于TMD层的生长和欧姆接触，其中天然形成了石墨烯/ TMD异质结构。石墨烯的存在会不可预测地影响2D CDW导体中的CDW顺序。这项工作报告了石墨烯/ NbSe ₂异质结构中2H-NbSe ₂层的CDW跃迁。拉曼光谱的演化表明NbSe ₂的CDW相变温度（T _CDW）。当被石墨烯封端时，其急剧下降。通过扫描隧道显微镜测量可以确认诱发的异常短程CDW状态。研究结果提出了通过监测A _1g模式的线形来确定T _CDW的新标准。同时，还发现了2D波段作为观察CDW过渡的指示器。第一性原理计算表明，界面电子掺杂通过阻止2H-NbSe ₂的晶格畸变来抑制CDW态。非同寻常的随机CDW晶格暗示了对许多集体电子状态形成机理的深刻洞察，并在调制多功能器件方面具有巨大潜力。

更新日期：2020-11-12

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