Poster presentation

Twisted bilayer zigzag-graphene nanoribbon junctions with tunable edge states
Dongfei Wang¹, D. Bao¹, Q. Zheng¹, C. Wang¹, S. Wang², P. Fan¹, S. Mishra², L. Tao¹, Y. Xiao¹, L. Huang¹, X. Feng³, K. Müllen⁴, Y. Zhang¹, R. Fasel², P. Ruffieux², S. Du¹, H. Gao¹

1 Institute of Physics & University of Chinese Academy of Sciences, 100190, Beijing, China
2 Nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600, Dübendorf, Switzerland
3 Center for Advancing Electronics Dresden (cfaed) and Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, 01062, Dresden, Germany
4 Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany

Manipulating the edge state of zigzag graphene nanoribbons (ZGNRs) is a long-standing and interesting topic in surface science. On the one hand, understanding the novel physics regarding the edges of these materials, such as magnetism, the strong correlation effect and the topological effect, is fundamentally important. On the other hand, there are great opportunities for fabricating advanced nanodevices such as spin filters or beam splitters based on ZGNRs [1]. Recent intensive investigations on two-dimensional (2D) twistronics have inspired the idea of edge-state manipulation by stacking one ZGNR on top of another, namely, a twisted bilayer one-dimensional (1D) system. In such a system, the lateral stacking offset serves as an additional parameter for modulating the resulting material properties.

We construct and characterize twisted bilayer zigzag graphene nanoribbon (TBZGNR) systems on a Au(111) surface using scanning tunneling microscopy. A detailed analysis of three prototypical orthogonal TBZGNR junctions exhibiting different stacking offsets by means of scanning tunneling spectroscopy reveals emergent near-zero-energy states. From a comparison with DFT calculations, we conclude that the emergent edge states originate from the formation of flat bands whose energy and spin degeneracy are highly tunable with the stacking offset. Our work highlights fundamental differences between 2D and 1D twistronics and spurs further investigation of twisted one-dimensional systems [2].

Figure 1: Tunning the edge state of bilayer graphene nanoribbon by twisting angle (a) and stacking offset (b).

[1] Sanz, S.et al., Phys. Rev. Lett. 129, 037701 (2022)
[2] D. Wang et al., Nat. Commun. 14, 1018 (2023)