Alkali-induced rich properties in graphene nanoribbons: Chemical bonding

TL;DR

This paper investigates the electronic and magnetic properties of alkali-adsorbed graphene nanoribbons using first-principles calculations, revealing how adatom characteristics influence their rich physical behaviors.

Contribution

It provides a detailed analysis of how alkali adatoms affect the electronic structure, magnetism, and chemical bonding in graphene nanoribbons, highlighting the role of orbital hybridization and edge configurations.

Findings

Presence of adatom-dominated conduction bands

Edge-dependent magnetic ordering (antiferromagnetic, ferromagnetic, non-magnetic)

Distinct peaks in density of states due to energy dispersions

Abstract

The alkali-adsorbed graphene nanoribbons exhibit the feature-rich electronic and magnetic properties. From the first-principles calculations, there are only few adatom-dominated conduction bands, and the other conduction and valence bands are caused by carbon atoms. A lot of free electrons are revealed in the occupied alkali- and carbon-dependent conduction bands. Energy bands are sensitive to the concentration, distribution and kind of adatom and the edge structure, while the total linear free carrier density only relies on the first one. These mainly arise from a single $s-2p_z$ orbital hybridization in the adatom-carbon bond. Specifically, zigzag systems can present the anti-ferromagnetic ordering across two edges, ferromagnetic ordering along one edge and non-magnetism, being reflected in the edge-localized energy bands with or without spin splitting. The diverse energy dispersions contribute many special peaks in density of states. The critical chemical bonding and the distinct spin configuration could be verified from the experimental measurements.