Higher-Order Band Topology in Twisted Moiré Superlattice
- 12 February 2021
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 126 (6), 066401
- https://doi.org/10.1103/physrevlett.126.066401
Abstract
The two-dimensional (2D) twisted bilayer materials with van der Waals coupling have ignited great research interests, paving a new way to explore the emergent quantum phenomena by twist degree of freedom. Generally, with the decreasing of twist angle, the enhanced interlayer coupling will gradually flatten the low-energy bands and isolate them by two high-energy gaps at zero and full filling, respectively. Although the correlation and topological physics in the low-energy flat bands have been intensively studied, little information is available for these two emerging gaps. In this Letter, we predict a 2D second-order topological insulator (SOTI) for twisted bilayer graphene and twisted bilayer boron nitride in both zero and full filling gaps. Employing a tight-binding Hamiltonian based on first-principles calculations, three unique fingerprints of 2D SOTI are identified, that is, nonzero bulk topological index, gapped topological edge state, and in-gap topological corner state. Most remarkably, the 2D SOTI exists in a wide range of commensurate twist angles, which is robust to microscopic structure disorder and twist center, greatly facilitating the possible experimental measurement. Our results not only extend the higher-order band topology to massless and massive twisted moiré superlattice, but also demonstrate the importance of high-energy bands for fully understanding the nontrivial electronics.Keywords
Funding Information
- National Natural Science Foundation of China (11774325, 21603210)
- National Key Research and Development Program of China (2017YFA0204904)
- Fundamental Research Funds for the Central Universities
- H2020 European Research Council (ERC-2015-AdG-694097)
- Simons Foundation
- Grupos Consolidados (IT1249-19)
- Advanced Imaging of Matter (SFB925)
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