• 文献标题:   Mechanism for Anomalous Hall Ferromagnetism in Twisted Bilayer Graphene
  • 文献类型:   Article
  • 作  者:   BULTINCK N, CHATTERJEE S, ZALETEL MP
  • 作者关键词:  
  • 出版物名称:   PHYSICAL REVIEW LETTERS
  • ISSN:   0031-9007 EI 1079-7114
  • 通讯作者地址:   Univ Calif Berkeley
  • 被引频次:   33
  • DOI:   10.1103/PhysRevLett.124.166601
  • 出版年:   2020

▎ 摘  要

Motivated by the recent observation of an anomalous Hall effect in twisted bilayer graphene, we use a lowest Landau level model to understand the origin of the underlying symmetry-broken correlated state. This effective model is rooted in the occurrence of Chern bands which arise due to the coupling between the graphene device and its encapsulating substrate. Our model exhibits a phase transition from a spin-valley polarized insulator to a partial or fully valley unpolarized metal as the bandwidth is increased relative to the interaction strength, consistent with experimental observations. In sharp contrast to standard quantum Hall ferromagnetism, the Chern number structure of the flat bands precludes an instability to an intervalley coherent phase, but allows for an excitonic vortex lattice at large interaction anisotropy.