title: Inhibiting Klein Tunneling in a Graphene p-n Junction without an External Magnetic Field.
abstract: We study by first-principles calculations a densely packed island of organic molecules (F_{4}TCNQ) adsorbed on graphene. We find that with electron doping the island naturally forms a p-n junction in the graphene sheet. For example, a doping level of ∼3×10^{13}  electrons per cm^{2} results in a p-n junction with an 800 meV electrostatic potential barrier. Unlike in a conventional p-n junction in graphene, in the case of the junction formed by an adsorbed organic molecular island we expect that the Klein tunneling is inhibited, even without an applied external magnetic field. Here Klein tunneling is inhibited by the ferromagnetic order that spontaneously occurs in the molecular island upon doping. We estimate that the magnetic barrier in the graphene sheet is around 10 mT.
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.|Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Hyungju
authors.initials: H
authors.lastname: Oh
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.|Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Sinisa
authors.initials: S
authors.lastname: Coh
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.|Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.|Korea Institute for Advanced Study, Hoegiro 85, Seoul 02455, Korea.
authors.forename: Young-Woo
authors.initials: YW
authors.lastname: Son
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.|Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Marvin L
authors.initials: ML
authors.lastname: Cohen