Enhanced Screening in Chemically Functionalized Graphene

TL;DR

This paper investigates how hydrogen adatoms in graphene influence electronic screening, revealing a complex behavior with increased dielectric response but no metallic divergence, and introduces a new length scale related to localization.

Contribution

It provides a detailed analysis of impurity-induced screening effects in functionalized graphene, linking the Anderson localization length to screening suppression.

Findings

Increased dielectric function with midgap states

No metallic divergence at small momentum transfer

Emergence of a localization length scale

Abstract

Resonant scatterers such as hydrogen adatoms can strongly enhance the low energy density of states in graphene. Here, we study the impact of these impurities on the electronic screening. We find a two-faced behavior: Kubo formula calculations reveal an increased dielectric function $\varepsilon$ upon creation of midgap states but no metallic divergence of the static $\varepsilon$ at small momentum transfer $q\to 0$. This bad metal behavior manifests also in the dynamic polarization function and can be directly measured by means of electron energy loss spectroscopy. A new length scale $l_c$ beyond which screening is suppressed emerges, which we identify with the Anderson localization length.