Engineering Flat Bands in Graphene-Based Materials

Twisted bilayer graphene exhibits emergent correlated phenomena such as superconductivity, Mott insulat-ing state etc. The experimental electronic structure, in particular the evolution flat band near the Fermi energy, is critical for understanding the fundamental physics. In this talk, I will present our recent progress on the flat band electronic structure of various graphene-based materials using NanoARPES. In particular, by combining AFM which allows to determine the twist angle accurately with NanoARPES, we have succeeded in revealing the evolution of the flat band electronic structure across the magic angle and extracting the interlay tunneling parameters. Moreover, the remote bands also carry important information about the interlayer interaction. We also observe a switching of the spectral weight for the remote bands, highlighting the critical role of lattice relaxations [1]. I will also represent our progress on the electronic band structure of an asymmetrically-stacked twisted van der Waals heterostructure, where the flat band is further tunable by a bias voltage [2]. Flat bans in other graphene-based structures will also be discussed.<br/><br/>References<br/>[1] Qian Li⁺, Hongyun Zhang⁺, Yijie Wang, Wanying Chen, Changhua Bao, Qinxin Liu, Tianyun Lin, Shuai Zhang, Haoxiong Zhang, Kenji Watanabe, Takashi Taniguchi, Jose Avila, Pavel Dudin, Qunyang Li, Pu Yu, Wenhui Duan, Zhida Song and Shuyun Zhou*, “Spectroscopic evolution of flat band and critical role of lattice relaxations in twisted bilayer graphene”, Nat. Mater. (2024) https://www.nature.com/articles/s41563-024-01858-4<br/>[2] Qian Li⁺, Hongyun Zhang⁺ et al., “Observation of dichotomic field-tunable electronic structure in twisted monolayer-bilayer graphene”, Nat. Commun. 15, 3737 (2024)