中国物理B ›› 2023, Vol. 32 ›› Issue (11): 117201-117201.doi: 10.1088/1674-1056/acddcf

• • 上一篇    下一篇

Spontaneous isospin polarization and quantum Hall ferromagnetism in a rhombohedral trilayer graphene superlattice

Xiangyan Han(韩香岩)1, Qianling Liu(刘倩伶)1, Ruirui Niu(牛锐锐)1, Zhuangzhuang Qu(曲壮壮)1, Zhiyu Wang(王知雨)1, Zhuoxian Li(李卓贤)1, Chunrui Han(韩春蕊)2,3,†, Kenji Watanabe4, Takashi Taniguchi4, Zizhao Gan(甘子钊)1, and Jianming Lu(路建明)1,‡   

  1. 1 State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China;
    2 Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China;
    3 University of Chinese Academy of Sciences, Beijing 100049, China;
    4 National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
  • 收稿日期:2023-04-12 修回日期:2023-06-08 接受日期:2023-06-13 出版日期:2023-10-16 发布日期:2023-10-26
  • 通讯作者: Chunrui Han, Jianming Lu E-mail:hanchunrui@ime.ac.cn;jmlu@pku.edu.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11974027 and 62275265), the National Key Research and Development Program of China (Grant Nos. 2019YFA0307800 and 2021YFA1400100), and Beijing Natural Science Foundation (Grant Nos. Z190011 and 4222084).

Spontaneous isospin polarization and quantum Hall ferromagnetism in a rhombohedral trilayer graphene superlattice

Xiangyan Han(韩香岩)1, Qianling Liu(刘倩伶)1, Ruirui Niu(牛锐锐)1, Zhuangzhuang Qu(曲壮壮)1, Zhiyu Wang(王知雨)1, Zhuoxian Li(李卓贤)1, Chunrui Han(韩春蕊)2,3,†, Kenji Watanabe4, Takashi Taniguchi4, Zizhao Gan(甘子钊)1, and Jianming Lu(路建明)1,‡   

  1. 1 State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China;
    2 Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China;
    3 University of Chinese Academy of Sciences, Beijing 100049, China;
    4 National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan
  • Received:2023-04-12 Revised:2023-06-08 Accepted:2023-06-13 Online:2023-10-16 Published:2023-10-26
  • Contact: Chunrui Han, Jianming Lu E-mail:hanchunrui@ime.ac.cn;jmlu@pku.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11974027 and 62275265), the National Key Research and Development Program of China (Grant Nos. 2019YFA0307800 and 2021YFA1400100), and Beijing Natural Science Foundation (Grant Nos. Z190011 and 4222084).

摘要: Moiré superlattices in van der Waals heterostructures have recently attracted enormous interests, due to the highly controllable electronic correlation that gives rise to superconductivity, ferromagnetism, and nontrivial topological properties. To gain a deep understanding of such exotic properties, it is essential to clarify the broken symmetry between spin and valley flavors which universally exists in these ground states. Here in a rhombohedral trilayer graphene crystallographically aligned with a hexagonal boron nitride, we report various kinds of symmetry-breaking transition tuned by displacement fields (D) and magnetic fields: (i) While it is well known that a finite D can enhance correlation to result in correlated insulators at fractional fillings of a flat band, we find the correlation gap emerges before the flavor is fully filled at a positive D, but the sequence is reversed at a negative D. (ii) Around zero D, electronic correlation can be invoked by narrow Landau levels, leading to quantum Hall ferromagnetism that lifts all the degeneracies including not only spin and valley but also orbital degrees of freedom. Our result unveils the complication of transitions between symmetry-breaking phases, shedding light on the mechanisms of various exotic phenomena in strongly correlated systems.

关键词: rhombohedral trilayer graphene, moiré superlattice, symmetry breaking, flavor polarization, van Hove singularity, quantum Hall ferromagnetism

Abstract: Moiré superlattices in van der Waals heterostructures have recently attracted enormous interests, due to the highly controllable electronic correlation that gives rise to superconductivity, ferromagnetism, and nontrivial topological properties. To gain a deep understanding of such exotic properties, it is essential to clarify the broken symmetry between spin and valley flavors which universally exists in these ground states. Here in a rhombohedral trilayer graphene crystallographically aligned with a hexagonal boron nitride, we report various kinds of symmetry-breaking transition tuned by displacement fields (D) and magnetic fields: (i) While it is well known that a finite D can enhance correlation to result in correlated insulators at fractional fillings of a flat band, we find the correlation gap emerges before the flavor is fully filled at a positive D, but the sequence is reversed at a negative D. (ii) Around zero D, electronic correlation can be invoked by narrow Landau levels, leading to quantum Hall ferromagnetism that lifts all the degeneracies including not only spin and valley but also orbital degrees of freedom. Our result unveils the complication of transitions between symmetry-breaking phases, shedding light on the mechanisms of various exotic phenomena in strongly correlated systems.

Key words: rhombohedral trilayer graphene, moiré superlattice, symmetry breaking, flavor polarization, van Hove singularity, quantum Hall ferromagnetism

中图分类号:  (Electronic transport in graphene)

  • 72.80.Vp
73.40.-c (Electronic transport in interface structures) 73.21.Cd (Superlattices)