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arXiv · 1805.03790

Heterostrain engineering on twisted graphene bilayer around the first magic angle

Jia-Bin Qiao·Long-Jing Yin·Lin He
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Abstract

Very recently, twisted graphene bilayer (TGB) around the first magic angle 1.1° has attracted much attention for the realization of exotic quantum states, such as correlated insulator behavior and unconventional superconductivity. Here we elaborately studied a series of TGBs around the first magic angle engineered by heterostrain, where each layer is strained independently. Our experiment indicated that a moderate heterostrain enables the structural evolution from the small-angle TGB ( ~ 1.5°) to the strained magic-angle TGB (θ ~ 1.1°), exhibiting the characteristic low-energy flat bands. The heterostrain can even drive the system into highly strained tiny-angle TGBs (θ << 1.1°) with large deformed tetragonal superlattices, where a unique network of topological helical edge states emerges. Furthermore, the predicted domain wall modes, which are strongly localized and result in hexagon-triangle-mixed frustrated lattice derived from Kagome lattice, are observed in the strained tiny-angle TGBs.

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Jia-Bin Qiao, Long-Jing Yin, Lin He. 2018-10-07. Heterostrain engineering on twisted graphene bilayer around the first magic angle. https://doi.org/10.1103/physrevb.98.235402

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