Bilayer twisting as a mean to isolate connected flat bands in a kagome lattice through Wigner crystallization

• 作者: Jing Wu Yue-E Xie Ming-Xing Chen Jia-Ren Yuan Xiao-Hong Yan Sheng-Bai Zhang Yuan-Ping Chen
• 来源期刊: 中国物理B（英文版）
• 年，卷（期）: 2021,（7）
• 所属期刊栏目: SPECIAL TOPIC—Twistronics
• 页码范围: 6-12
• 页数: 7页
• 语种: 英文
• DOI: 10.1088/1674-1056/abd7d6

摘要

The physics of fiat band is novel and rich but difficult to access.In this regard,recently twisting of bilayer van der Waals (vdW)-bounded two-dimensional (2D) materials has attracted much attention,because the reduction of Brillouin zone will eventually lead to a diminishing kinetic energy.Alternatively,one may start with a 2D kagome lattice,which already possesses flat bands at the Fermi level,but unfortunately these bands connect quadratically to other (dispersive)bands,leading to undesirable effects.Here,we propose,by first-principles calculation and tight-binding modeling,that the same bilayer twisting approach can be used to isolate the kagome flat bands.As the starting kinetic energy is already vanishingly small,the interlayer vdW potential is always sufficiently large irrespective of the twisting angle.As such the electronic states in the (connected) fiat bands become unstable against a spontaneous Wigner crystallization,which is expected to have interesting interplays with other flat-band phenomena such as novel superconductivity and anomalous quantum Hall effect.