Low Temperature Insulating State in hBN-Encapsulated Multilayer Graphene

Bilayer graphene is susceptible to strong electron-electron interactions at charge neutrality, leading to the possibility for spontaneous symmetry breaking and the associated opening of a gap at low temperatures, even in the absence of any external fields [1]. Recent experiments confirm this possibility for Bernal stacked graphene layers of thickness up to 8 layers [2-4], but this physics is only observed via transport in suspended devices of the highest quality. Here, we present evidence for the opening of a gap at low temperatures in multilayer graphene systems which are encapsulated in hBN. The dielectric environment of hBN not only alleviates the requirement for suspension, but also poses constraints on the nature of the interactions. Our results provide new insights into the insulating state of multilayer graphene systems, and help to facilitate their fabrication for potential applications.

[1] Y. Barlas, R. Côté, K. Nomura, A. H. MacDonald, Phys. Rev. Lett. 101, 097601 (2008).
[2] R. T. Weitz, M. T. Allen, B. E. Feldman, J. Martin, A. Yacoby, Science 330, 812–816 (2010).
[3] Y. Nam, D.-K. Ki, M. Koshino, E. McCann, A. F. Morpurgo, 2D Mater. 3, 045014 (2016).
[4] Youngwoo Nam, Dong-Keun Ki, David Soler-Delgado, Alberto F. Morpurgo, Science 362, 324-328 (2018).