物理学进展

物理学进展 ›› 2023, Vol. 43 ›› Issue (5): 151-160.doi: 10.13725/j.cnki.pip.2023.05.003

所属专题： 2023年, 第43卷

• • 上一篇    

转角双层石墨烯中的势杂质效应 

刘泽众1, 王 达1,2   

  1. 1. 南京大学物理学院，固体微结构物理国家重点实验室，南京 210093 2. 人工微结构科学与技术协同创新中心，南京大学，南京 210093
  • 出版日期:2023-10-20 发布日期:2023-10-23

Potential Impurity Effect in Twisted Bilayer Graphene

LIU Ze-zhong1 , WANG Da1,2   

  1. 1. National Laboratory of Solid State Microstructures & School of Physics, Nanjing University, Nanjing, 210093, China 2. Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China 
  • Online:2023-10-20 Published:2023-10-23

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摘要：

近年来，平带在转角双层石墨烯（TBG）中的发现引起了越来越多的关注。在这项工作中， 我们报告了我们对这个平带系统中杂质效应的研究，这对于真实材料来说是一个重要问题。通过 采用 Lanczos 递归方法，我们求解了杂质附近的局域态密度（LDOS）。我们发现，对于大尺寸的 杂质，一系列束缚态在杂质内部形成，LDOS 中平带所对应的峰在杂质边界附近被压制，而在杂 质内部由于杂质势的作用而发生平移。随着杂质尺寸变小，其对平带的影响变弱，这符合其大尺寸 Wannier 函数的预期。这个特性与通常具有小尺寸局域 Wannier 轨道的平带系统有所不同，表明 TBG 中的平带对小尺寸杂质更加稳定。 

关键词: 杂质效应, 转角双层石墨烯, 局域态密度, 平带

Abstract:

Flat band has attracted more and more interest in recent years, motivated by its discovery in twisted bilayer graphene (TBG). In this work, we report our study of the impurity effect on this flat band system, which is an important issue for real materials. Employing the Lanczos recursive method, we solve the local density of states (LDOS) around a potential impurity. We find for large impurity size, a series of bound states are formed inside the impurity, and the flat band peak in LDOS is suppressed near the impurity boundary and shifted by the impurity potential deep inside the impurity. As the impurity size becomes smaller, the effect on the flat band becomes weaker, as anticipated from the large scale of the underlying Wannier function. This property distinguishes with the usual flat band systems with small localized Wannier orbitals, and indicates the flat band in TBG is more stable against small-size impurities. 

Key words: impurity effect, twisted bilayer graphene, local density of states, flat band

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