title: Optimal Hubbard models for materials with nonlocal Coulomb interactions: graphene, silicene, and benzene.
abstract: To understand how nonlocal Coulomb interactions affect the phase diagram of correlated electron materials, we report on a method to approximate a correlated lattice model with nonlocal interactions by an effective Hubbard model with on-site interactions U(*) only. The effective model is defined by the Peierls-Feynman-Bogoliubov variational principle. We find that the local part of the interaction U is reduced according to U(*)=U-V[over ¯], where V[over ¯] is a weighted average of nonlocal interactions. For graphene, silicene, and benzene we show that the nonlocal Coulomb interaction can decrease the effective local interaction by more than a factor of 2 in a wide doping range.
authors.affiliation: Institut für Theoretische Physik, Universität Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany. mschueler@itp.uni-bremen.de
authors.forename: M
authors.initials: M
authors.lastname: Schüler
authors.forename: M
authors.initials: M
authors.lastname: Rösner
authors.forename: T O
authors.initials: TO
authors.lastname: Wehling
authors.forename: A I
authors.initials: AI
authors.lastname: Lichtenstein
authors.forename: M I
authors.initials: MI
authors.lastname: Katsnelson