科学家实现扭曲双层石墨烯结构域内和域间局部扭曲角变化的可视化

本期文章：《中国物理快报》：Volume 41 Issue 3

近日，中国科学院物理研究所北京凝聚态物理国家研究中心的高鸿钧及其研究团队取得一项新进展。经过不懈努力，他们实现扭曲双层石墨烯结构域内和域间局部扭曲角变化的可视化。相关研究成果已于2024年3月6日在国际知名学术期刊《中国物理快报》上发表。

本文利用扫描微波阻抗显微镜(sMIM)直接观察了，扭曲双层石墨烯中局部扭曲角的变化和量子态的角度依赖演化。空间分辨的sMIM测量结果显示，局部扭曲角发生了明显的变化，在某些情况下，在几微米范围内约为0.3°。变化不仅发生在跨域边界时，有时也发生在单个域内。

此外，平带的满填充密度在跨越域边界时发生了超过2×1011 cm-2的变化，与扭曲角的非均匀性一致。相关的Chern绝缘子随着扭曲角的变化而变化，随着偏离魔角的增大而逐渐减弱，最终消失。这一发现表明扭曲角在塑造量子态分布和存在方面的关键作用，为推进扭曲二维材料的研究奠定了基础。

据悉，扭曲二维材料中的莫尔超晶格是研究工程量子现象的理想平台，它对扭曲角的全局值和空间非均匀性都非常敏感。然而，只有少数方法能够提供空间分辨的信息来表征局部扭曲角分布。

附：英文原文

Title: Visualizing the Local Twist Angle Variation within and between Domains of Twisted Bilayer Graphene

Author: Jiawei Hu, Shiyu Zhu Qianying Hu, Yunhao Wang, Chengmin Shen, Haitao Yang, Xiaoshan Zhu, Qing Huan, Yang Xu, and Hong-Jun Gao

Issue&Volume: 2024-03-06

Abstract: Moiré superlattices in twisted two-dimensional materials have emerged as ideal platforms for engineering quantum phenomena, which are highly sensitive to twist angles, including both the global value and the spatial inhomogeneity. However, only a few methods provide spatial-resolved information for characterizing local twist angle distribution. Here we directly visualize the variations of local twist angles and angle-dependent evolutions of the quantum states in twisted bilayer graphene by scanning microwave impedance microscopy (sMIM). Spatially resolved sMIM measurements reveal a pronounced alteration in the local twist angle, approximately 0.3° over several micrometers in some cases. The variation occurs not only when crossing domain boundaries but also occasionally within individual domains. Additionally, the full-filling density of the flat band experiences a change of over 2×1011 cm-2 when crossing domain boundaries, aligning consistently with the twist angle inhomogeneity. Moreover, the correlated Chern insulators undergo variations in accordance with the twist angle, gradually weakening and eventually disappearing as the deviation from the magic angle increases. Our findings signify the crucial role of twist angles in shaping the distribution and existence of quantum states, establishing a foundational cornerstone for advancing the study of twisted two-dimensional materials.

DOI: 10.1088/0256-307X/41/3/037401

Source: https://cpl.iphy.ac.cn/10.1088/0256-307X/41/3/037401

期刊信息
Chinese Physics Letters：《中国物理快报》，创刊于1985年。隶属于中国物理学会，最新IF：3.5

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