Transport in Twisted Bilayer Graphene at Extreme Angles

Two misaligned layers of graphene exhibit intriguing transport properties that depend drastically on the twist angle. At very large twists, the system behaves similar to two decoupled graphene layers. Upon reduction of the angle, the graphene layers begin to couple, leading to a decrease in Fermi velocity. At a magical angle of 1.1°, superconductivity emerges [1]. Finally, at tiny twist angles, large regions of strongly coupled bilayer graphene dominate the transport. By gating, these regions can become insulating leading to a triangular network of topological channels [2]. An intriguing probe for transport phenomena in graphene consists in the formation of an electronic Fabry-Pérot interferometer [3,4]. P-n junctions serve as semi-transparent mirrors and exhibit relativistic phenomena such as Klein-tunneling and we discuss how they can be used to access the interesting physics twisted bilayer graphene at tiny [5] and at very large twist angles.

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[3] P. Rickhaus et. al. Nat. Commun. 4, 1 (2013)
[4] P. Rickhaus et. al., Nat. Commun. 6, 6470 (2015)
[5] P. Rickhaus, J. Wallbank, S. Slizovskiy, R. Pisoni, H. Overweg, Y. Lee, M. Eich, M.-H. Liu, K. Watanabe, T. Taniguchi, T. Ihn, and K. Ensslin, 10.1021/acs.nanolett.8b02387 (2018).