Local Moment Formation and Kondo Effect in Defective Graphene

TL;DR

This paper investigates how vacancies in graphene can host local magnetic moments and exhibit the Kondo effect, considering complex hybridization effects and various physical parameters influencing these phenomena.

Contribution

The study introduces a detailed model that accounts for vacancy reconstruction, non-planarity, and singular hybridization, revealing new impurity phases affecting magnetic and Kondo behaviors.

Findings

Singular hybridization enhances local moment formation.

Multiple impurity phases influence the Kondo effect.

Vacancy properties depend on Coulomb interactions, doping, and symmetry breaking.

Abstract

We study the local moment formation and the Kondo effect at single-atom vacancies in Graphene. We develop a model accounting for the vacancy reconstruction as well as non-planarity effects induced by strain and/or temperature. Thus, we find that the dangling $\sigma$ orbital localized at the vacancy is allowed to strongly hybridize with the $\pi$-band since the scattering with the vacancy turns the hybridization into singular function of the energy ($\sim [|\epsilon| \ln^2 \epsilon/D]^{-1}$, $D\sim$ the bandwidth). This leads to several new types of impurity phases, which control the magnitude of the vacancy magnetic moment and the possibility of Kondo effect depending on the strength of the local Coulomb interactions, the Hund's rule coupling, the doping level, and the degree of particle-symmetry breaking.