paper

Coulomb charging energy of vacancy-induced states in graphene

arXiv:1605.03469 · doi:10.1103/PhysRevB.94.075114

Abstract

Vacancies in graphene have been proposed to give rise to -like magnetism in carbon materials, a conjecture which has been supported by recent experimental evidence. A key element in this "vacancy magnetism" is the formation of magnetic moments in vacancy-induced electronic states. In this work we compute the charging energy of a single-vacancy generated localized state for bulk graphene and graphene ribbons. We use a tight-binding model to calculate the dependency of the charging energy on the amplitudes of the localized wave function on the graphene lattice sites. We show that for bulk graphene scales with the system size as , confirming the predictions in the literature, based on heuristic arguments. In contrast, we find that for realistic system sizes is of the order of eV, a value that is orders of magnitude higher than the previously reported estimates. Finally, when edges are considered, we show that is very sensitive to the vacancy position with respect to the graphene flake boundaries. In the case of armchair nanoribbons, we find a strong enhancement of in certain vacancy positions as compared to the value for vacancies in bulk graphene.

13 pages, 9 figures

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