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arXiv 1702.03501cond-mat.mes-hallcond-mat.mtrl-sci
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石墨烯Moiré超晶格中Van Hove奇点周围电子-电子相互作用的证据

Evidence of electron-electron interactions around Van Hove singularities of a graphene Moiré superlattice

Si-Yu Li, Ke-Qin Liu, Long-Jin Yin, Wen-Xiao Wang, Wei Yan, Xu-Qin Yang, Jun-Kai Yang, Haiwen Liu, Hua Jiang, Lin He

摘要:

在掺杂到其态密度(DOS)的范霍夫奇点(VHS)的石墨烯单层中,预测了各种新的和有趣的关联态。然而,由于它们的大能量距离(3eV),通过门控或化学掺杂来调节费米能量以达到石墨烯的VHS是非常困难的。因此,这些相关的状态,产生于强电子-电子相互作用的影响,在VHS,仍然是实验难以捉摸的。在这里,我们通过扫描隧道显微镜测量扭曲双层石墨烯(TBG)的VHS周围的电子-电子相互作用的实验证据。通过在两个相邻的石墨烯片之间引入小的扭曲角,我们能够产生任意接近费米能量的低能VHS。观察到了VHS的分裂,并直观地观察到了VHS周围电子态的对称性破缺。这些结果实验证明了电子-电子相互作用对TBG的VHS周围的电子性质的重要影响,因此为考虑多体相互作用的石墨烯系统的进一步理论和实验研究提供了动力。

英文摘要:

A variety of new and interesting correlated states have been predicted in graphene monolayer doped to Van Hove singularities (VHSs) of its density-of-state (DOS). However, tuning the Fermi energy to reach a VHS of graphene by either gating or chemical doping is prohibitively difficult, owning to their large energy distance (3 eV). Therefore, these correlated states, which arise from effects of strong electron-electron interactions at the VHSs, have remained experimentally elusive. Here, we report experimental evidences of electron-electron interactions around the VHSs of a twisted bilayer graphene (TBG) through scanning tunneling microscopy measurements. By introducing a small twisted angle between two adjacent graphene sheets, we are able to generate low-energy VHSs arbitrarily approaching the Fermi energy. The split of the VHSs are observed and the symmetry breaking of electronic states around the VHSs are directly visualized. These results experimentally demonstrate the important effects of electron-electron interactions on electronic properties around the VHSs of the TBG, therefore providing motivation for further theoretical and experimental studies in graphene systems with considering many-body interactions.

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