Lu Qiangsheng, Le Congcong, Zhang Xiaoqian, Cook Jacob, He Xiaoqing, Zarenia Mohammad, Vaninger Mitchel, Miceli Paul F, Singh David J, Liu Chang, Qin Hailang, Chiang Tai-Chang, Chiu Ching-Kai, Vignale Giovanni, Bian Guang
Department of Physics and Astronomy, University of Missouri, Columbia, MO, 65211, USA.
RIKEN Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), Wako, Saitama, 351-0198, Japan.
Adv Mater. 2022 Jul;34(26):e2200625. doi: 10.1002/adma.202200625. Epub 2022 May 23.
Tuning interactions between Dirac states in graphene has attracted enormous interest because it can modify the electronic spectrum of the 2D material, enhance electron correlations, and give rise to novel condensed-matter phases such as superconductors, Mott insulators, Wigner crystals, and quantum anomalous Hall insulators. Previous works predominantly focus on the flat band dispersion of coupled Dirac states from different twisted graphene layers. In this work, a new route to realizing flat band physics in monolayer graphene under a periodic modulation from substrates is proposed. Graphene/SiC heterostructure is taken as a prototypical example and it is demonstrated experimentally that the substrate modulation leads to Dirac fermion cloning and, consequently, the proximity of the two Dirac cones of monolayer graphene in momentum space. Theoretical modeling captures the cloning mechanism of the Dirac states and indicates that moiré flat bands can emerge at certain magic lattice constants of the substrate, specifically when the period of modulation becomes nearly commensurate with the supercell of graphene. The results show that epitaxial single monolayer graphene on suitable substrates is a promising platform for exploring exotic many-body quantum phases arising from interactions between Dirac electrons.
调控石墨烯中狄拉克态之间的相互作用引起了极大的兴趣，因为它可以改变这种二维材料的电子能谱，增强电子关联，并产生诸如超导体、莫特绝缘体、维格纳晶体和量子反常霍尔绝缘体等新型凝聚态相。先前的工作主要集中在不同扭曲石墨烯层耦合狄拉克态的平带色散上。在这项工作中，提出了一种在衬底的周期性调制下在单层石墨烯中实现平带物理的新途径。以石墨烯/碳化硅异质结构作为典型例子，通过实验证明衬底调制导致狄拉克费米子克隆，进而导致单层石墨烯的两个狄拉克锥在动量空间中靠近。理论建模捕捉到了狄拉克态的克隆机制，并表明在衬底的某些神奇晶格常数下会出现莫尔平带，特别是当调制周期与石墨烯的超胞几乎相称时。结果表明，在合适衬底上的外延单原子层石墨烯是探索由狄拉克电子相互作用产生的奇异多体量子相的一个有前景的平台。
