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arXiv · 2609.39986

Atomic-Scale Imaging of Lattice Relaxation and Topological Flat Bands in Helical Trilayer Graphene

Shudan Jiang·Zonglin Li·Yu Gu·Liang Liu·Dandan Guan·Yaoyi Li·Hao Zheng·Canhua Liu·Kenji Watanabe·Takashi Taniguchi·Shengwei Jiang·Xiaoxue Liu·Zhiwen Shi·Guorui Chen·Jinfeng Jia·Tingxin Li·Can Li·Shiyong Wang
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Abstract

Helical trilayer graphene (HTG) has emerged as a highly tunable moire quantum material that hosts strong electronic correlations and nontrivial band topology. However, the atomic-scale lattice structure and local electronic properties have remained largely unexplored. Here we present a comprehensive real-space study of HTG using a combination of scanning near-field optical microscopy and low-temperature scanning tunneling microscopy. We directly image supermoire lattice relaxation, revealing large triangular domains separated by sharp domain walls, as well as stripe domains connected by smoothly varying boundaries. Atomic-scale spectroscopy uncovers flat bands with a honeycomb electronic texture and one-dimensional boundary states confined to domain walls. By systematically varying the twist angle, we identify a magic angle of approximately 1.9°, substantially larger than the 1.6 degree predicted by theory. Our results establish a direct microscopic link between lattice relaxation and flat bands in HTG.

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Shudan Jiang, Zonglin Li, Yu Gu, Liang Liu, Dandan Guan, Yaoyi Li, Hao Zheng, Canhua Liu, Kenji Watanabe, Takashi Taniguchi, Shengwei Jiang, Xiaoxue Liu, Zhiwen Shi, Guorui Chen, Jinfeng Jia, Tingxin Li, Can Li, Shiyong Wang. 2026-09-30. Atomic-Scale Imaging of Lattice Relaxation and Topological Flat Bands in Helical Trilayer Graphene. https://arxiv.org/abs/2609.39986

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