Tailoring Magnetism of Graphene Nanoflakes via Tip-Controlled Dehydrogenation

Atomically precise graphene nanoflakes called nanographenes have emerged as a promising platform to realize carbon magnetism. Their ground state spin configuration can be anticipated by Ovchinnikov-Lieb rules based on the mismatch of 7V electrons from two sublattices. While rational geometrical design achieves specific spin configurations, further direct control over the 7V electrons offers a desirable extension for efficient spin manipulations and potential quantum device operations. To this end, we apply a site-specific dehydrogenation using a scanning tunneling microscope tip to nanographenes deposited on a Au(111) substrate, which shows the capability of precisely tailoring the underlying 7V-electron system and therefore efficiently manipulating their magnetism. Through first-principles calculations and tight-binding meanfield-Hubbard modeling, we demonstrate that the dehydrogenation-induced Au-C bond formation along with the resulting hybridization between frontier 7V orbitals and Au substrate states effectively eliminate the unpaired 7V electron. Our results establish an efficient technique for controlling the magnetism of nanographenes.