Coulomb-Engineered Heterojunctions and Dynamical Screening in Transition Metal Dichalcogenide Monolayers

TL;DR

This paper investigates how the dielectric environment influences the electronic properties of monolayer transition metal dichalcogenides (TMDCs), demonstrating the potential for non-invasive Coulomb engineering of heterojunctions with nanoscale precision.

Contribution

It provides a quantitative analysis of dielectric and dynamic screening effects in TMDCs, introducing a multi-scale model for Coulomb-engineered heterojunctions with nanoscale band gap control.

Findings

Symmetric, rigid-shift-like band gap modulations observed.

Short-range self-energies enable effective multi-scale modeling.

Nanoscale band gap modulations are achievable with structured substrates.

Abstract

The manipulation of two-dimensional materials via their dielectric environment offers novel opportunities to control electronic as well as optical properties and allows to imprint nanostructures in a non-invasive way. Here we asses the potential of monolayer semiconducting transition metal dichalcogenides (TMDCs) for Coulomb engineering in a material realistic and quantitative manner. We compare the response of different TMDC materials to modifications of their dielectric surrounding, analyze effects of dynamic substrate screening, i.e. frequency dependencies in the dielectric functions, and discuss inherent length scales of Coulomb-engineered heterojunctions. We find symmetric and rigid-shift-like quasi-particle band-gap modulations for both, instantaneous and dynamic substrate screening. From this we derive short-ranged self energies for an effective multi-scale modeling of Coulomb engineered heterojunctions composed of an homogeneous monolayer placed on a spatially structured substrate. For these heterojunctions, we show that band gap modulations on the length scale of a few lattice constants are possible rendering external limitations of the substrate structuring more important than internal effects. We find that all semiconducting TMDCs are similarly well suited for these external and non-invasive modifications.