Quantum capacitive coupling between large-angle twisted graphene layers

TL;DR

This paper develops a quantum capacitance model for large-angle twisted bilayer graphene, revealing strong capacitive coupling effects and proposing a method to induce tunable bandgaps in bilayer graphene for advanced device applications.

Contribution

It introduces a self-consistent quantum capacitance model for decoupled graphene layers, extending it to twisted bilayer graphene under magnetic fields and proposing a tunable bandgap induction method.

Findings

Good agreement between simulations and experiments on capacitive coupling.

Identification of strong capacitive effects in large-angle twisted bilayer graphene.

Proposal of a new experiment to induce tunable bandgaps in bilayer graphene.

Abstract

Large-angle twisted bilayer graphene (tBLG) is known to be electronically decoupled due to the spatial separation of the Dirac cones corresponding to individual graphene layers in the reciprocal space. The close spacing between the layers causes strong capacitive coupling, opening possibilities for applications in atomically thin devices. Here, we present a self-consistent quantum capacitance model for the electrostatics of decoupled graphene layers, and further generalize it to deal with decoupled tBLG at finite magnetic field and large-angle twisted double bilayer graphene at zero magnetic field. We probe the capacitive coupling through the conductance, showing good agreement between simulations and experiments for all the systems considered. We also propose a new experiment utilizing the decoupling effect to induce a huge and tunable bandgap in bilayer graphene by applying a moderately low bias. Our model can be extended to systems composed of decoupled graphene multilayers as well as non-graphene systems, opening a new realm of quantum-capacitively coupled materials.