Heterostrain-induced flat bands in untwisted bilayer graphene

Twist-induced lattice misalignment of bilayer graphene leads to moiré patterns that generate electronic flat bands with strongly correlated electronic states, but it still requires a sophisticated process to precisely control the twist angle. Here, we propose a different way to generate hexagonal moirés in bilayer graphene by uniaxially stretching the two layers along two distinct armchair directions, respectively. The heterostrain-induced moiré gives rise to flat bands near the Fermi level due to the deformation-induced equivalent misaligned angle between two graphene layers, featuring an electronic equivalence of twisted bilayer graphene. We demonstrate the flat bands at a heterostrain of 2.1%, equivalent to the first magic angle of 1.05°. Yet, a slight shift of Dirac point from K point due to the uniaxial strain splits the flat bands into two van Hove singularity peaks that are separated by 18 meV and located above and below the Fermi level, respectively. Our results suggest a potential way to control the electronic strong correlation in bilayer graphene of natural stacking.