Tuning commensurability in twisted van der Waals bilayers

• 成果类型: Article
• 署名作者: Li, Yanxing; Zhang, Fan; Ha, Viet-Anh; Lin, Yu-Chuan; Dong, Chengye; Gao, Qiang; Liu, Zhida; Liu, Xiaohui; Ryu, Sae Hee; Kim, Hyunsue; Jozwiak, Chris; Bostwick, Aaron; Watanabe, Kenji; Taniguchi, Takashi; Kousa, Bishoy; Li, Xiaoqin; Rotenberg, Eli; Khalaf, Eslam; Robinson, Joshua A.; Giustino, Feliciano; Shih, Chih-Kang
• 署名单位: University of Texas System; University of Texas Austin; University of Texas System; University of Texas Austin; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; National Yang Ming Chiao Tung University; United States Department of Energy (DOE); Lawrence Berkeley National Laboratory; National Institute for Materials Science
• 刊物名称: Nature
• ISSN/ISSBN: 0028-6878
• DOI: 10.1038/s41586-023-06904-w
• 发表日期: 2024-01-18
• 关键词: graphene; STATES

摘要

Moire superlattices based on van der Waals bilayers1-4 created at small twist angles lead to a long wavelength pattern with approximate translational symmetry. At large twist angles (theta t), moire patterns are, in general, incommensurate except for a few discrete angles. Here we show that large-angle twisted bilayers offer distinctly different platforms. More specifically, by using twisted tungsten diselenide bilayers, we create the incommensurate dodecagon quasicrystals at theta t = 30 degrees and the commensurate moire crystals at theta t = 21.8 degrees and 38.2 degrees. Valley-resolved scanning tunnelling spectroscopy shows disparate behaviours between moire crystals (with translational symmetry) and quasicrystals (with broken translational symmetry). In particular, the K valley shows rich electronic structures exemplified by the formation of mini-gaps near the valence band maximum. These discoveries demonstrate that bilayers with large twist angles offer a design platform to explore moire physics beyond those formed with small twist angles. Using valley-resolved scanning tunnelling spectroscopy, twisted WSe2 bilayers are studied, including incommensurate dodecagon quasicrystals at 30 degrees and commensurate moire crystals at 21.8 degrees and 38.2 degrees.