Domino-like stacking order switching in twisted monolayer–multilayer graphene

• Published in: Nature materials Vol. 21; no. 6; pp. 621 - 626
• Main Authors: Zhang, Shuai, Xu, Qiang, Hou, Yuan, Song, Aisheng, Ma, Yuan, Gao, Lei, Zhu, Mengzhen, Ma, Tianbao, Liu, Luqi, Feng, Xi-Qiao, Li, Qunyang
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-06-2022; Nature Publishing Group
• Subjects: 639/301/357/537; 639/925/918/1053; Atomic force microscopy; Biomaterials; Chemistry and Materials Science; Condensed Matter Physics; Ferromagnetism; Fine structure; Graphene; Letter; Materials Science; Microscopy; Monolayers; Multilayers; Nanotechnology; Optical and Electronic Materials; Reconstruction; Solitary waves; Stacking; Switching
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/s41563-022-01232-2

Atomic reconstruction has been widely observed in two-dimensional van der Waals structures with small twist angles
1
–
7
. This unusual behaviour leads to many novel phenomena, including strong electronic correlation, spontaneous ferromagnetism and topologically protected states
1
,
5
,
8
–
14
. Nevertheless, atomic reconstruction typically occurs spontaneously, exhibiting only one single stable state. Using conductive atomic force microscopy, here we show that, for small-angle twisted monolayer–multilayer graphene, there exist two metastable reconstruction states with distinct stacking orders and strain soliton structures. More importantly, we demonstrate that these two reconstruction states can be reversibly switched, and the switching can propagate spontaneously in an unusual domino-like fashion. Assisted by lattice-resolved conductive atomic force microscopy imaging and atomistic simulations, the detailed structure of the strain soliton networks has been identified and the associated propagation mechanism is attributed to the strong mechanical coupling among solitons. The fine structure of the bistable states is critical for understanding the unique properties of van der Waals structures with tiny twists, and the switching mechanism offers a viable means for manipulating their stacking states.
The interface stacking order of twisted graphene can be actively flipped between locally stable states using a mechanical impulse, and this flipping propagates spontaneously through the network in a domino-like fashion.