Electronic transport in low-angle twisted bilayer graphene

Abstract

Graphene is a two-dimensional material with exotic electronic, optical and mechanical properties. By stacking two layers of graphene together with a small rotation angle between them, a superlattice of arbitrarily large size can be formed. The hybridization of the electronic states in the two layers can result in reduced Fermi velocity, van Hove singularities and a gapped band structure. In this work, a novel tear-and-stack technique is developed to reliably produce twisted bilayer graphene with controlled angle, and electronic transport measurements of the resulting high-quality samples are performed and discussed. We discover novel insulating states that purely results from the moiŕe superlattice band structure. The magnetotransport properties of these insulating states are studied and indicate that these states have different structure with those in either graphene or AB-stacked bilayer graphene; it shows a non-monotonous change of Fermi surface area which agrees with theoretical calculations. The results point toward a new pathway for graphene-related physics and material research.