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arXiv · 2111.10410

Unconventional Flat Chern Bands and 2$e$ Charges in Skyrmionic Moir\'e Superlattices

Yifei Guan·Oleg V. Yazyev·Alexander Kruchkov
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Abstract

The interplay of topological characteristics in real space and reciprocal space can lead to the emergence of unconventional topological phases. In this Letter, we implement a novel mechanism for generating higher-Chern flat bands on the basis of twisted bilayer graphene (TBG) coupled to topological magnetic structures in the form of the skyrmion lattice. In particular, we discover a scenario for generating $|C|=2$ dispersionless electronic bands when the skyrmion periodicity and the moir\'e periodicity are matched. Following the Wilczek argument, the statistics of the charge-carrying excitations in this case is \textit{bosonic}, characterized by electronic charge $Q =2e$, that is \textit{even} in units of electron charge $e$. The required skyrmion coupling strength triggering the topological phase transition is realistic, with its threshold estimated as low as 4~meV. The Hofstadter butterfly spectrum of this phase is different resulting in an unexpected quantum Hall conductance sequence $\pm \frac{2 e^2}{h}, \ \pm \frac{4 e^2}{h}, ...$ for TBG with skyrmion order.

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Yifei Guan, Oleg V. Yazyev, Alexander Kruchkov. 2021-11-19. Unconventional Flat Chern Bands and 2$e$ Charges in Skyrmionic Moir\'e Superlattices. https://arxiv.org/abs/2111.10410

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