Electron-Electron Interactions on the Edge States of Graphene: A Many Body Configuration Interaction Study

TL;DR

This study investigates electron-electron interactions in graphene nanoribbons using many-body configuration interaction methods, revealing edge-specific magnetic states, charge distribution, and optical properties relevant for electronic and optoelectronic applications.

Contribution

It provides a detailed many-body analysis of edge states in graphene nanoribbons, highlighting differences between zigzag and armchair types and their electronic and optical behaviors.

Findings

Zigzag GNRs have high spin ground states due to edge effects.

Both GNR types are insulating but can conduct via edge channels.

Optical properties differ between zigzag and armchair GNRs.

Abstract

We have studied zigzag and armchair graphene nano ribbons (GNRs), described by the Hubbard Hamiltonian using quantum many body configuration interaction methods. Due to finite termination, we find that the bipartite nature of the graphene lattice gets destroyed at the edges making the ground state of the zigzag GNRs a high spin state, whereas the ground state of the armchair GNRs remains a singlet. Our calculations of charge and spin densities suggest that, although the electron density prefers to accumulate on the edges, instead of spin polarization, the up and down spins prefer to mix throughout the GNR lattice. While the many body charge gap results in insulating behavior for both kinds of GNRs, the conduction upon application of electric field is still possible through the edge channels because of their high electron density. Analysis of optical states suggest differences in quantum efficiency of luminescence for zigzag and armchair GNRs, which can be probed by simple experiments.