Twisted bilayer graphene is created by slightly rotating the two crystal networks in bilayer graphene with respect to each other. For small twist angles, the material undergoes a self-organized lattice reconstruction, leading to the formation of a periodically repeated domain^1,2,3. The resulting superlattice modulates the vibrational^3,4 and electronic^5,6 structures within the material, leading to changes in the behaviour of electron–phonon coupling^7,8 and to the observation of strong correlations and superconductivity⁹. However, accessing these modulations and understanding the related effects are challenging, because the modulations are too small for experimental techniques to accurately resolve the relevant energy levels and too large for theoretical models to properly describe the localized effects. Here we report hyperspectral optical images, generated by a nano-Raman spectroscope¹⁰, of the crystal superlattice in reconstructed (low-angle) twisted bilayer graphene. Observations of the crystallographic structure with visible light are made possible by the nano-Raman technique, which reveals the localization of lattice dynamics, with the presence of strain solitons and topological points¹ causing detectable spectral variations. The results are rationalized by an atomistic model that enables evaluation of the local density of the electronic and vibrational states of the superlattice. This evaluation highlights the relevance of solitons and topological points for the vibrational and electronic properties of the structures, particularly for small twist angles. Our results are an important step towards understanding phonon-related effects at atomic and nanometric scales, such as Jahn–Teller effects¹¹ and electronic Cooper pairing^12,13,14, and may help to improve device characterization¹⁵ in the context of the rapidly developing field of twistronics¹⁶.

扭曲的双层石墨烯是通过将双层石墨烯中的两个晶体网络相对于彼此轻微旋转而产生的。对于小扭转角，材料会经历自组织晶格重建，从而形成周期性重复的域^1,2,3。由此产生的超晶格调制材料内的振动^3,4和电子^5,6结构，导致电子 - 声子耦合^7,8的行为发生变化，并观察到强相关性和超导性⁹. 然而，访问这些调制和理解相关效应具有挑战性，因为调制太小，实验技术无法准确解析相关能级，而理论模型太大，无法正确描述局部效应。在这里，我们报告了由纳米拉曼光谱仪¹⁰生成的重建（低角度）扭曲双层石墨烯中的晶体超晶格的高光谱光学图像。纳米拉曼技术使得用可见光观察晶体结构成为可能，该技术揭示了晶格动力学的局部化，存在应变孤子和拓扑点¹导致可检测的光谱变化。结果通过原子模型合理化，该模型能够评估超晶格的电子和振动状态的局部密度。该评估强调了孤子和拓扑点与结构的振动和电子特性的相关性，特别是对于小扭转角。我们的结果是朝着理解原子和纳米尺度的声子相关效应迈出的重要一步，例如 Jahn-Teller 效应¹¹和电子库珀配对^12,13,14，并且可能有助于在快速发展的背景下改善器件表征¹⁵ 16.twistronics领域^_