Strain-induced flatbands in large-angle twisted bilayer graphene

Abstract

Twisted bilayer graphene (TBG) has attracted widespread attention due to its unique and tunable properties. In this study, we systematically investigate the effects of in-plane biaxial tensile strain on the electronic properties of TBG with a twist angle greater than the magic angle by the tight-binding approach. Our results reveal that the energy bands near the Fermi level gradually narrow as the strain increases, resulting in a continuous decrease in Fermi velocity and the formation of flatbands. Especially, TBG with a larger twist angle requires a greater critical strain to achieve flatbands. The strain-induced flatbands exhibit a narrow bandwidth and vanishing Fermi velocity, similar to the band structures observed at the magic angle. Furthermore, the formation of these flatbands can be understood by the enhancement of charge localization and the competition between kinetic energy and interlayer hybridization energy during the strain process. Our findings present a potential avenue to produce flatbands in large-angle TBG, paving the way for further exploration and application in advanced materials science.