Wigner crystallization at graphene edges

TL;DR

This paper demonstrates that Wigner crystallization occurs at graphene zigzag edges at high electron densities, influenced by flat-band structures, affecting edge magnetization and spin correlations.

Contribution

It reveals the occurrence of Wigner crystallization at high densities on graphene edges using many-body techniques, highlighting the role of flat-band structures in electron localization.

Findings

Wigner crystallization occurs at densities up to 0.8 nm^{-1}.

Crystallization influences edge magnetization and spin correlations.

Edge spin states transition from full polarization to magnetic coupling as density decreases.

Abstract

Using many-body configuration interaction techniques we show that Wigner crystallization occurs at the zigzag edges of graphene at surprisingly high electronic densities up to $0.8$ $\mbox{nm}^{-1}$. In contrast with one-dimensional electron gas, the flat-band structure of the edge states makes the system interaction dominated, facilitating the electronic localization. The resulting Wigner crystal manifests itself in pair-correlation functions, and evolves smoothly as the edge electron density is lowered. We also show that the crystallization affects the magnetization of the edges. While the edges are fully polarized when the system is charge neutral (i.e. high density), above the critical density, the spin-spin correlations between neighboring electrons go through a smooth transition from antiferromagnetic to magnetic coupling as the electronic density is lowered.