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Résumé : The physics of a carbon vacancy in graphene has been the subject of intense research since the early days of graphene. It was studied from various points of views: zero energy state (1), bound charge and its fractionalization (2,3), magnetism (4,5) and unusual Friedel oscillations (6). And yet the interrelation of all these is still not completely clear. In this presentation, I will review these results and explain how our recent discovery of a vortex in the bond order near the vacancy (7) (so-called Kekulé vortex) provides a unified framework to understand these seemingly disparate aspects of the carbon vacancy physics. I will show how that, in addition, this research has led to the recognition that the local density of states measured near defects is a topological observable. (1) Pereira, V. M., Guinea, F., Lopes dos Santos, J. M. B., Peres, N. M. R. Castro Neto, A. H. Disorder Induced Localized States in Graphene. Phys. Rev. Lett. 96, 036801 (2006). (2) Ducastelle, F. Electronic structure of vacancy resonant states in graphene: a critical review of the single-vacancy case. Phys. Rev. B 88, 075413 (2013) (3) Ovdat, O., Don, Y. & Akkermans, E. Vacancies in graphene: Dirac physics and fractional vacuum charges. Phys. Rev. B 102, 075109 (2020) (4) Yazyev, O. V. & Helm, L. Defect-induced magnetism in graphene. Phys. Rev. B 75, 125408 (2007). (5) González-Herrero, H. et al. Atomic-scale control of graphene magnetism by using hydrogen atoms. Science 352, 437–441 (2016). (6) Dutreix, C. et al. Measuring the Berry phase of graphene from wavefront dislocations in Friedel oscillations. Nature 574, 219–222 (2019). (7) Guan, Y et al. Observation of Kekulé vortices around hydrogen adatoms in graphene. 15, 2927 (2024)
