Abstract
We study the edge spectrum of twisted sheets of single layer and bilayer graphene in cases where the continuum model predicts a valley Chern insulator - an insulating state in which the occupied moiré mini-bands from each valley have a net Chern number, but both valleys together have no net Chern number, as required by time-reversal symmetry. In a simple picture, such a state might be expected to have chiral valley polarized counterpropagating edge states. We present results from exact diagonalization of the tight-binding model of commensurate structures in the ribbon geometry. We find that for both the single-layer and bilayer moiré ribbons robust edge modes are generically absent. We attribute this lack of edge modes to the fact that the edge induces valley mixing.
Original language | English |
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Article number | 085138 |
Journal | Physical Review B |
Volume | 107 |
Issue number | 8 |
DOIs | |
State | Published - Feb 15 2023 |
Bibliographical note
Publisher Copyright:© 2023 American Physical Society.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics