Topological Domain-Wall States from Umklapp Scattering in Twisted Bilayer Graphene.
basic_science · Level V
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- Record sourced from PubMed, PMID 41314802.
- Also identified by DOI 10.1021/acs.nanolett.5c04006.
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Abstract
Twistronics, harnessing interlayer rotation to tailor electronic states in van der Waals materials, has predominantly focused on small-angle regimes. Here, we unveil the pivotal role of intervalley Umklapp scattering in large-angle twisted bilayer graphene, which governs low-energy physics and drives unconventional band topology. By constructing symmetry-constrained effective <i>k</i>·<i>p</i> models for ±21.8°-twisted bilayers, we demonstrate how structural chirality imprints distinct electronic responses. The <i>D</i><sub>6</sub> configuration exhibits a gapped spectrum with chiral interlayer coupling, while the <i>D</i><sub>3</sub>-symmetric stacking configuration displays semimetallic behavior. Crucially, chirality inversion creates topological domain-wall states, which manifest as counterpropagating pseudospin modes at interfaces between oppositely twisted regions. These states, absent in untwisted bilayers, emerge from a Jackiw-Rebbi-like mechanism tied to chirality reversal. Atomistic simulations confirm these topological states and demonstrate their robustness against symmetry-breaking perturbations. The interplay between twist-induced chirality and topology opens new pathways for engineering domain-wall states in twisted materials.