Impurity band induced by point defects in graphene

TL;DR

This paper demonstrates that point defects in graphene create an impurity band with a semi-circular density of states, which enhances conductivity and supports ferromagnetism, challenging the independent scatterer approximation.

Contribution

It reveals that correlated point defects induce an impurity band in graphene, significantly affecting its electronic and magnetic properties, a novel insight into defect interactions.

Findings

Defects induce an impurity band with Wigner semi-circle density of states.

Impurity band enhances graphene's conductivity to about 4e^2/h.

Impurity band supports ferromagnetism with magnetic moments near 1μ_B per defect.

Abstract

It is pointed out that point defects on graphene are strongly correlated and can not be treated as independent scatters. In particular, for large on-site defect potential, it is shown that defects induce an impurity band with density of state characterized by the Wigner semi-circle law. We find that the impurity band enhances conductivity to the order of $4 e^2 /h $ and explains the absence of strong localization. Furthermore,the impurity band supports ferromagnetism with the induced magnetic moment approaching 1$\mu_B$ per defect in the limit of infinite quasi-particle lifetime.