Strain-Engineered Correlated Phases and Band Flattening in Graphene via Stressor Arrays (Part 1)

In the design of graphene-based devices, strain offers an additional degree of freedom to tune the lattice structure and modify band structure. Here, we demonstrate a deterministic method to strain two-dimensional materials using process induced stressor arrays on graphene/hBN, and conduct scanning tunnelling microscopy/spectroscopy (STM/STS) to investigate the strain-induced phenomena. Our square thin-film stressors generate a sharp tensile strain gradient at their edges and a gradual strain gradient farther from their edges, and our STM results quantitatively identify the spatially anisotropic strains, in both magnitude and direction. We use STM topography to survey the changes to the graphene/hBN Moiré and track the change in lattice angle around the corners of the stressors. As we approach the stressor, we observe that the hexagon Moiré of graphene/hBN becomes more distorted. Moving closer to the corners of the stressor, we measure Moiré exhibiting ~1nm oscillating stripe corrugation associated with 50T of pseudomagnetic field and 7 ± 2% strain. At various regions with different strain gradients, our STM/STS data reveals different strain-induced phenomena, including band flattening and correlated gap opening. This work establishes a new route to exploring strain-induced correlated physics in graphene and provides a platform for next-generation device fabrication with precise control of strain-induced phenomena.