Mechanical and Electronic Properties of Graphene under Periodically Modulated Strain

We present a novel approach to create an effective 2D lateral heterostructure – by periodic modulation of lattice strain. We engineer extreme (>10%) strain in graphene by draping it over large Cu step edges. Analogous to a draped tablecloth, nanoscale periodic ripples arise as graphene is pinned and pulled by the contact forces of the substrate. The ripples are characterized by large variations in carbon-carbon bond length. Such variations directly impact electronic coupling between atoms, which in one graphene ripple can be as different as in two different materials. The result is a single graphene sheet which effectively acts as an electronic superlattice in which novel electronic states arise at the interfaces. Such intense, highly inhomogeneous fields create a new electronic quantization distinct from the usual Landau quantization observed in uniform fields, and their nanoscale periodicity creates a novel electronic system which can aid in the realization of various theoretical proposals including valley filters, snake states and electron optics in graphene and other 2D materials.

Ref: Banerjee et. al., Nano Lett. 2020, 20, 5, 3113–3121 (2020)