Origin of band gaps in graphene on hexagonal boron nitride
  Recent progress in preparing well controlled 2D van der Waals heterojunctions has opened up a new frontier in materials physics. In this paper we address the intriguing energy gaps that are sometimes observed when a graphene sheet is placed on a hexagonal boron nitride substrate, demonstrating that they are produced by an interesting interplay between structural and electronic properties, including electronic many-body exchange interactions. Our theory is able to explain the observed gap behavior by accounting first for the structural relaxation of graphene's carbon atoms when placed on a boron nitride substrate and then for the influence of the substrate on low-energy $\pi$-electrons located at relaxed carbon atom sites. The methods we employ can be applied to many other van der Waals heterojunctions. 
Jeil Jung, Ashley DaSilva, Allan H. MacDonald, Shaffique Adam
cond-mat.mes-hall