title: Femtomagnetism in graphene induced by core level excitation of organic adsorbates.
abstract: We predict the induction or suppression of magnetism in the valence shell of physisorbed and chemisorbed organic molecules on graphene occurring on the femtosecond time scale as a result of core level excitations. For physisorbed molecules, where the interaction with graphene is dominated by van der Waals forces and the system is non-magnetic in the ground state, numerical simulations based on density functional theory show that the valence electrons relax towards a spin polarized configuration upon excitation of a core-level electron. The magnetism depends on efficient electron transfer from graphene on the femtosecond time scale. On the other hand, when graphene is covalently functionalized, the system is magnetic in the ground state showing two spin dependent mid gap states localized around the adsorption site. At variance with the physisorbed case upon core-level excitation, the LUMO of the molecule and the mid gap states of graphene hybridize and the relaxed valence shell is not magnetic anymore.
authors.affiliation: Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 55 - 20125 Milano, Italia.
authors.forename: Abhilash
authors.initials: A
authors.lastname: Ravikumar
authors.affiliation: Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 55 - 20125 Milano, Italia.
authors.forename: Anu
authors.initials: A
authors.lastname: Baby
authors.affiliation: Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 55 - 20125 Milano, Italia.
authors.forename: He
authors.initials: H
authors.lastname: Lin
authors.affiliation: Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 55 - 20125 Milano, Italia.
authors.forename: Gian Paolo
authors.initials: GP
authors.lastname: Brivio
authors.affiliation: Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via Cozzi 55 - 20125 Milano, Italia.|Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria, 16 - 20133 Milano, Italia.
authors.forename: Guido
authors.initials: G
authors.lastname: Fratesi