Quantum capacitance and transport modeling in decoupled twisted graphene layers

Alina Mrenca-Kolasinska^1,2*, Peter Rickhaus³, Giulia Zheng³, Klaus Richter⁴, Thomas Ihn³, Klaus Ensslin³, Ming-Hao Liu¹

¹Department of Physics, National Cheng-Kung University, Tainan, Taiwan
²Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Cracow, Poland
³Solid State Physics Laboratory, ETH Zurich, Zurich, Switzerland
⁴Institut fur Theoretische Physik, Universitat Regensburg, Regensburg, Germany

* Presenter:Alina Mrenca-Kolasinska, email:alina.mrenca@fis.agh.edu.pl

Bilayer graphene consists of two graphene monolayers at a small spacing. When there is a twist between the two graphene lattices, the Brillouin zones of the two layers become rotated with respect to each other, and for a large twist angle this leads to the separation of the Dirac cones of both layers [1]. Due to large momentum difference, scattering between the two layers is suppressed, which makes the two layers decoupled electronically. However, they are electrostatically coupled because the electric charge on one layer causes an effective gating of the other layer. This argument can be extended to large-angle twisted double bilayer graphene (tdBLG) and other multilayer graphene systems.
We develop a self-consistent electrostatic model for decoupled twisted bilayer graphene (tBLG) system and apply it for quantum transport simulations in dual-gated tBLG, observing Fabry-Perot resonances in low magnetic field and the Landau levels spectrum at strong magnetic field. The self-consistent model is also extended to tdBLG. For both systems we obtain excellent agreement between the transport measurement and simulation [2]. The models can be generalized to other materials hosting Dirac fermions or described by other dispersion relations.

[1] P. Rickhaus et al., Sci. Adv. 6, eaay8409 (2020).
[2] A. Mrenca-Kolasinska et al., arXiv:2110.00907 [cond-mat.mes-hall].

Keywords: quantum capacitance, twisted bilayer graphene, quantum transport , Landau levels, Fabry-Perot interferometer