Local Density of States Modulated by Strain in Marginally Twisted Bilayer Graphene

In marginally twisted bilayer graphene, the Moiré pattern consists of the maximized AB (BA) stacking regions, minimized AA stacking regions and triangular networks of domain walls. Here we realize the strain-modulated electronic structures of marginally twisted bilayer graphene by scanning tunneling microscopy/spectroscopy and density functional theory (DFT) calculations. The experimental data show four peaks near the Fermi energy at the AA regions. DFT calculations indicate that the two new peaks closer to the Fermi level may originate from the intrinsic heterostrain and the electric field implemented by back gate is likely to account for the observed shift of the four peaks. Furthermore, the dI/dV map across Moiré patterns with different strain strengths exhibits a distinct appearance of the helical edge states.