挠曲电
材料科学
凝聚态物理
超晶格
双层石墨烯
范德瓦尔斯力
石墨烯
双层
扭转
压电
压电响应力显微镜
光电子学
纳米技术
铁电性
物理
化学
复合材料
分子
量子力学
电介质
几何学
生物化学
膜
数学
作者
Yuhao Li,Xiao Wang,Deqi Tang,Xi Wang,Kenji Watanabe,Takashi Taniguchi,Daniel R. Gamelin,David Cobden,Matthew Yankowitz,Xiaodong Xu,Jiangyu Li
标识
DOI:10.1002/adma.202105879
摘要
Moiré superlattices of 2D materials with a small twist angle are thought to exhibit appreciable flexoelectric effect, though unambiguous confirmation of their flexoelectricity is challenging due to artifacts associated with commonly used piezoresponse force microscopy (PFM). For example, unexpectedly small phase contrast (≈8°) between opposite flexoelectric polarizations is reported in twisted bilayer graphene (tBG), though theoretically predicted value is 180°. Here a methodology is developed to extract intrinsic moiré flexoelectricity using twisted double bilayer graphene (tDBG) as a model system, probed by lateral PFM. For small twist angle samples, it is found that a vectorial decomposition is essential to recover the small intrinsic flexoelectric response at domain walls from a large background signal. The obtained threefold symmetry of commensurate domains with significant flexoelectric response at domain walls is fully consistent with the theoretical calculations. Incommensurate domains in tDBG with relatively large twist angles can also be observed by this technique. A general strategy is provided here for unraveling intrinsic flexoelectricity in van der Waals moiré superlattices while providing insights into engineered symmetry breaking in centrosymmetric materials.
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