Strain-induced modulation of Dirac cones and van Hove singularities in twisted graphene bilayer

By means of atomistic tight-binding calculations, we investigate the effects of uniaxial strain on the electronic bandstructure of twisted graphene bilayer. We find that the bandstructure is dramatically deformed and the degeneracy of the bands is broken by strain. As a conseqence, the number of Dirac cones can double and the van Hove singularity points are separated in energy. The dependence of these effects on the strength of strain, its applied direction and the twist angle is carefully clarified. As an important result, we demonstrate that the position of van Hove singularities can be modulated by strain, suggesting the possibility of observing this phenomenon at low energy in a large range of twist angle (i.e., larger than $10^\circ$). Unfortunately, these interesting/important phenomena have not been clarified in the previous works based on the continuum approximation. While they are in good agreement with available experiments, our results provide a detailed understanding of the strain effects on the electronic properties and may motivate other investigations of electronic transport in this type of graphene lattice.