Missing atom as a source of carbon magnetism

Introducing vacancies in graphene-like systems by irradiation has been shown to be an efficient method to vary its mechanical behavior, tune its electronic properties and even to induce magnetism in otherwise non-magnetic samples [1-2]. While the role played by these vacancies as single entities has been extensively addressed by theory [3-6], experimental data available refer to statistical properties of the whole heterogeneous collection of vacancies generated in the irradiation process. Here, by artificially generating isolated vacancies on a graphite surface and measuring their local density of states on the atomic scale, we have shown how single vacancies modify the electronic properties of this graphene-like system [7]. Our scanning tunneling microscopy experiments, complemented by tight binding calculations, reveal the presence of a sharp electronic resonance at the Fermi energy around each single graphite vacancy, which implies a dramatic reduction of the charge carriers' mobility and can be associated with the formation of local magnetic moments. Finally, we have extended our investigations to other graphene systems. \\[4pt] [1] P. Esquinazi, D. Spemann, R. H\"{o}hne, A. Setzer, K.-H. Han and T. Butz, \textit{Phys. Rev. Lett.} \textbf{91}, 227201 (2003).\\[0pt] [2] A. V. Krasheninnikov and F. Banhart, \textit{Nature Materials} \textbf{6}, 723 (2007)\\[0pt] [3] V. M. Pereira, F. Guinea, J. M. Lopes dos Santos, N. M. R. Peres and A. H. Castro Neto, \textit{Phys. Rev. Lett.} \textbf{96}, 036801 (2006)\\[0pt] [4] P. O. Lehtinen, A. S. Foster, Y. C. Ma, A. V. Krasheninnikov and R. M. Nieminen , \textit{Phys. Rev. Lett.} \textbf{93}, 187202 (2004).\\[0pt] [5] J. J. Palacios, J. Fern\'{a}ndez-Rossier and L. Brey, \textit{Phys Rev. B} \textbf{77}, 195428 (2008)\\[0pt] [6]. O. V.Yazyev, \textit{Phys}.\textit{ Rev. Lett.} \textbf{101}, 037203 (2008).\\[0pt] [7] M. M. Ugeda I. Brihuega, F. Guinea and J. M. G\'{o}mez Rodr\'{\i}guez, \textit{Phys. Rev. Lett }\textbf{104}, 096804 (2010)