Out-of-plane dielectric susceptibility of graphene in twistronic and Bernal bilayers

TL;DR

This paper investigates how the out-of-plane dielectric polarizability of monolayer graphene affects the electrostatics of bilayer graphene, comparing theoretical calculations with experimental data for Bernal and twisted bilayers.

Contribution

It provides a detailed comparison of the out-of-plane dielectric susceptibility of graphene from density functional theory and experimental measurements, enhancing understanding of bilayer electrostatics.

Findings

Monolayer polarizability in tBLG is well described by α_exp = 10.8 ų.

Effective out-of-plane dielectric susceptibility is ε_z = 2.5.

Results agree with experimental data on electron density and Landau level pinning.

Abstract

We describe how the out-of-plane dielectric polarizability of monolayer graphene influences the electrostatics of bilayer graphene -- both Bernal (BLG) and twisted (tBLG). We compare the polarizability value computed using density functional theory with the output from previously published experimental data on the electrostatically controlled interlayer asymmetry potential in BLG and data on the on-layer density distribution in tBLG. We show that monolayers in tBLG are described well by polarizability $\alpha_{exp} = 10.8 \unicode{x212B}^3$ and effective out-of-plane dielectric susceptibility $\epsilon_z = 2.5$, including their on-layer electron density distribution at zero magnetic field and the inter-layer Landau level pinning at quantizing magnetic fields.