# Internal screening and dielectric engineering in magic-angle twisted bilayer graphene

## TL;DR

This paper investigates how internal screening and dielectric environment influence electronic interactions in magic-angle twisted bilayer graphene, proposing dielectric engineering as a method to explore its quantum many-body states.

## Contribution

It reveals the role of interlayer coupling in enhancing internal screening and shows how dielectric environment effects depend on the electronic state, suggesting experimental dielectric tailoring.

## Key findings

- Interlayer coupling enhances internal screening.
- Dielectric environment effects depend on electronic state.
- Proposes dielectric environment engineering to study quantum states.

## Abstract

Magic-angle twisted bilayer graphene (MA-tBLG) has appeared as a tunable testing ground to investigate the conspiracy of electronic interactions, band structure, and lattice degrees of freedom to yield exotic quantum many-body ground states in a two-dimensional Dirac material framework. While the impact of external parameters such as doping or magnetic field can be conveniently modified and analyzed, the all-surface nature of the quasi-2D electron gas combined with its intricate internal properties pose a challenging task to characterize the quintessential nature of the different insulating and superconducting states found in experiments. We analyze the interplay of internal screening and dielectric environment on the intrinsic electronic interaction profile of MA-tBLG. We find that interlayer coupling generically enhances the internal screening. The influence of the dielectric environment on the effective interaction strength depends decisively on the electronic state of MA-tBLG. Thus, we propose the experimental tailoring of the dielectric environment, e.g. by varying the capping layer composition and thickness, as a promising pursuit to provide further evidence for resolving the hidden nature of the quantum many-body states in MA-tBLG.