We introduce a new method to continuously map inhomogeneities of a moiré lattice and apply it to large-area topographic images we measure on open-device twisted bilayer graphene (TBG). We show that the variation in the twist angle of a TBG device, which is frequently conjectured to be the reason for differences between devices with a supposed similar twist angle, is about ${0.08}^{\circ }$ around the average of ${2.02}^{\circ }$ over areas of several hundred nanometers, comparable to devices encapsulated between hexagonal boron nitride slabs. We distinguish between an effective twist angle and local anisotropy and relate the latter to heterostrain. Our results imply that for our devices, twist angle heterogeneity has an effect on the electronic structure roughly equal to that of local strain. The method introduced here is applicable to results from different imaging techniques and on different moiré materials.

中文翻译：

---

测量扭曲双层石墨烯的局部莫尔晶格异质性

我们介绍了一种连续绘制莫尔网格不均匀性的新方法，并将其应用于我们在开放设备扭曲双层石墨烯（TBG）上测量的大面积地形图像。我们表明，TBG设备的扭曲角变化（通常被认为是假设相似的扭曲角的设备之间存在差异的原因）大约为${0.08}^{\circ }$ 大约的平均值 ${2.02}^{\circ }$在数百纳米的面积上，与封装在六方氮化硼平板之间的器件相当。我们区分有效扭转角和局部各向异性，并将后者与异应变联系起来。我们的结果表明，对于我们的设备，扭曲角异质性对电子结构的影响大致等于局部应变。此处介绍的方法适用于来自不同成像技术和不同云纹材料的结果。