Second-order topological insulator in twisted bilayer graphene with small twist angle

doi:10.1088/1674-1056/adee03

中国物理B ›› 2025, Vol. 34 ›› Issue (11): 116801-116801.doi: 10.1088/1674-1056/adee03

Second-order topological insulator in twisted bilayer graphene with small twist angle

Fenghua Qi(戚凤华)¹, Jie Cao(曹杰)^2,†, Xingfei Zhou(周兴飞)^3,‡, and Guojun Jin(金国钧)^4,5,§

1 School of Electronic Engineering, Nanjing Xiaozhuang University, Nanjing 211171, China;
2 College of Mechanics and Engineering Science, Hohai University, Nanjing 210098, China;
3 New Energy Technology Engineering Laboratory of Jiangsu Province School of Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China;
4 School of Physics Science and Technology, Kunming University, Kunming 650214, China;
5 National Laboratory of Solid State Microstructures, Department of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, Chin

收稿日期:2025-05-24 修回日期:2025-06-24 接受日期:2025-07-10 发布日期:2025-11-10
通讯作者: Jie Cao, Xingfei Zhou, Guojun Jin E-mail:caojie@hhu.edu.cn;zxf@njupt.edu.cn;gjin@nju.edu.cn
基金资助:
This work was supported by the National Natural Science Foundation of China (Grant Nos. 12104232 and 12074156).

Second-order topological insulator in twisted bilayer graphene with small twist angle

Fenghua Qi(戚凤华)¹, Jie Cao(曹杰)^2,†, Xingfei Zhou(周兴飞)^3,‡, and Guojun Jin(金国钧)^4,5,§

1 School of Electronic Engineering, Nanjing Xiaozhuang University, Nanjing 211171, China;
2 College of Mechanics and Engineering Science, Hohai University, Nanjing 210098, China;
3 New Energy Technology Engineering Laboratory of Jiangsu Province School of Science, Nanjing University of Posts and Telecommunications, Nanjing 210023, China;
4 School of Physics Science and Technology, Kunming University, Kunming 650214, China;
5 National Laboratory of Solid State Microstructures, Department of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, Chin

Received:2025-05-24 Revised:2025-06-24 Accepted:2025-07-10 Published:2025-11-10
Contact: Jie Cao, Xingfei Zhou, Guojun Jin E-mail:caojie@hhu.edu.cn;zxf@njupt.edu.cn;gjin@nju.edu.cn
About author:2025-116801-250926.pdf
Supported by:
This work was supported by the National Natural Science Foundation of China (Grant Nos. 12104232 and 12074156).

摘要/Abstract

摘要： In recent years, the study of higher-order topological states and their material realizations has become a research frontier in topological condensed matter physics. We demonstrate that twisted bilayer graphene with small twist angles behaves as a second-order topological insulator possessing topological corner charges. Using a tight-binding model, we compute the topological band indices and corner states of finite-sized twisted bilayer graphene flakes. It is found that for any small twist angle, whether commensurate or incommensurate, the gaps both below and above the flat bands are associated with nontrivial topological indices. Our results not only extend the concept of second-order band topology to arbitrary small twist angles but also confirm the existence of corner states at acute-angle corners.

关键词: second-order topological insulators, twisted bilayer graphene

Abstract: In recent years, the study of higher-order topological states and their material realizations has become a research frontier in topological condensed matter physics. We demonstrate that twisted bilayer graphene with small twist angles behaves as a second-order topological insulator possessing topological corner charges. Using a tight-binding model, we compute the topological band indices and corner states of finite-sized twisted bilayer graphene flakes. It is found that for any small twist angle, whether commensurate or incommensurate, the gaps both below and above the flat bands are associated with nontrivial topological indices. Our results not only extend the concept of second-order band topology to arbitrary small twist angles but also confirm the existence of corner states at acute-angle corners.

Key words: second-order topological insulators, twisted bilayer graphene

中图分类号: (Superlattices)

68.65.Cd

73.20.At (Surface states, band structure, electron density of states) 03.65.Vf (Phases: geometric; dynamic or topological)

Fenghua Qi(戚凤华), Jie Cao(曹杰), Xingfei Zhou(周兴飞), and Guojun Jin(金国钧). Second-order topological insulator in twisted bilayer graphene with small twist angle[J]. 中国物理B, 2025, 34(11): 116801-116801.

Fenghua Qi(戚凤华), Jie Cao(曹杰), Xingfei Zhou(周兴飞), and Guojun Jin(金国钧). Second-order topological insulator in twisted bilayer graphene with small twist angle[J]. Chin. Phys. B, 2025, 34(11): 116801-116801.

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Second-order topological insulator in twisted bilayer graphene with small twist angle

Second-order topological insulator in twisted bilayer graphene with small twist angle

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