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arXiv · 2312.05487

Chiral symmetry breaking and topological charge of graphene nanoribbons

Hyun Cheol Lee·S. -R. Eric Yang
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Abstract

We explore the edge properties of rectangular graphene nanoribbons featuring two zigzag edges and two armchair edges. Although the self-consistent Hartree-Fock fields break chiral symmetry, our work demonstrates that graphene nanoribbons maintain their status as short-range entangled symmetry-protected topological insulators. The relevant symmetry involves combined mirror and time-reversal operations. In undoped ribbons displaying edge ferromagnetism, the band gap edge states with a topological charge form on the zigzag edges. An analysis of the anomalous continuity equation elucidates that this topological charge is induced by the gap term. In low-doped zigzag ribbons, where the ground state exhibits edge spin density waves, this topological charge appears as a nearly zero-energy edge mode. Our system is outside the conventional calssification for topological insulators.

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Hyun Cheol Lee, S. -R. Eric Yang. 2023-12-09. Chiral symmetry breaking and topological charge of graphene nanoribbons. https://arxiv.org/abs/2312.05487

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