Competition between spin and charge polarized states in nanographene ribbons with zigzag edges

TL;DR

This paper investigates how nearest neighbor Coulomb interactions influence nanographene ribbons with zigzag edges, revealing a competition between charge-polarized and spin-polarized states and the stabilization of a novel charge-separated state.

Contribution

It introduces the effect of nearest neighbor Coulomb interactions on edge states in nanographene ribbons, identifying a new charge-polarized state that competes with spin polarization.

Findings

Nearest neighbor Coulomb interaction stabilizes a charge-polarized state.

Charge-polarized state has a finite electric dipole moment.

External electric field stabilizes the charge-polarized state.

Abstract

Effects of the nearest neighbor Coulomb interaction on nanographene ribbons with zigzag edges are investigated using the extended Hubbard model within the unrestricted Hartree-Fock approximation. The nearest Coulomb interaction stabilizes a novel electronic state with the opposite electric charges separated and localized along both edges, resulting in a finite electric dipole moment pointing from one edge to the other. This charge-polarized state competes with the peculiar spin-polarized state caused by the on-site Coulomb interaction and is stabilized by an external electric field.