Emergence of Tertiary Dirac Points in Graphene Moiré Superlattices

Abstract

The electronic structure of a crystalline solid is largely determined by its\nlattice structure. Recent advances in van der Waals solids, artificial crystals\nwith controlled stacking of two-dimensional (2D) atomic films, have enabled the\ncreation of materials with novel electronic structures. In particular, stacking\ngraphene on hexagonal boron nitride (hBN) introduces moir\\'e superlattice that\nfundamentally modifies graphene's band structure and gives rise to secondary\nDirac points (SDPs). Here we find that the formation of a moir\\'e superlattice\nin graphene on hBN yields new, unexpected consequences: a set of tertiary Dirac\npoints (TDPs) emerge, which give rise to additional sets of Landau levels when\nthe sample is subjected to an external magnetic field. Our observations hint at\nthe formation of a hidden Kekul\\'e superstructure on top of the moir\\'e\nsuperlattice under appropriate carrier doping and magnetic fields.\n