Untwisted moiré bilayers from first principles

Twisted graphene devices exhibit very different properties, from ferromagnetism to superconductivity, depending on whether they are aligned or misaligned with encapsulating hBN layers. In order to untangle the effects of substrate alignment, we use classical force fields and first-principles DFT simulations to study moire physics in untwisted bilayers subject to biaxial heterostrain. We compare the atomic and electronic structure of heterostrained bilayer graphene to graphene/BN heterobilayers in order to isolate the impact of sublattice symmetry breaking. Out-of-plane corrugation is significantly enhanced in the heterostrained layers compared to their twisted counterparts, and the atomic relaxation pattern exhibits purely radial displacements.