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 { \pi}-electrons from two sublattices. While rational geometrical design achieves specific spin configurations, further direct control over the { \pi}-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 { \pi}-electron system and therefore efficiently manipulating their magnetism. Through first-principles calculations and tight-binding mean-field-Hubbard modelling, we demonstrate that the dehydrogenation-induced Au-C bond formation along with the resulting hybridization between frontier { \pi}-orbitals and Au substrate states effectively eliminate the unpaired { \pi}-electron. Our results establish an efficient technique for controlling the magnetism of nanographenes.
Categories: cond-mat.mtrl-sci cond-mat.mes-hall