title: Strength of effective Coulomb interactions in graphene and graphite.
abstract: To obtain an effective many-body model of graphene and related materials from first principles we calculate the partially screened frequency dependent Coulomb interaction. In graphene, the effective on-site (Hubbard) interaction is U(00)=9.3  eV in close vicinity to the critical value separating conducting graphene from an insulating phase emphasizing the importance of nonlocal Coulomb terms. The nearest-neighbor Coulomb interaction strength is computed to U(01)=5.5  eV. In the long-wavelength limit, we find the effective background dielectric constant of graphite to be ϵ=2.5 in very good agreement with experiment.
authors.affiliation: Institut für Theoretische Physik, Universität Hamburg, Hamburg, Germany.
authors.forename: T O
authors.initials: TO
authors.lastname: Wehling
authors.forename: E
authors.initials: E
authors.lastname: Saşıoğlu
authors.forename: C
authors.initials: C
authors.lastname: Friedrich
authors.forename: A I
authors.initials: AI
authors.lastname: Lichtenstein
authors.forename: M I
authors.initials: MI
authors.lastname: Katsnelson
authors.forename: S
authors.initials: S
authors.lastname: Blügel