title: Giant edge state splitting at atomically precise graphene zigzag edges.
abstract: Zigzag edges of graphene nanostructures host localized electronic states that are predicted to be spin-polarized. However, these edge states are highly susceptible to edge roughness and interaction with a supporting substrate, complicating the study of their intrinsic electronic and magnetic structure. Here, we focus on atomically precise graphene nanoribbons whose two short zigzag edges host exactly one localized electron each. Using the tip of a scanning tunnelling microscope, the graphene nanoribbons are transferred from the metallic growth substrate onto insulating islands of NaCl in order to decouple their electronic structure from the metal. The absence of charge transfer and hybridization with the substrate is confirmed by scanning tunnelling spectroscopy, which reveals a pair of occupied/unoccupied edge states. Their large energy splitting of 1.9 eV is in accordance with ab initio many-body perturbation theory calculations and reflects the dominant role of electron-electron interactions in these localized states.
authors.affiliation: Nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Shiyong
authors.identifier: 0000-0002-0004-7023
authors.initials: S
authors.lastname: Wang
authors.affiliation: Nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Leopold
authors.identifier: 0000-0002-1524-5903
authors.initials: L
authors.lastname: Talirz
authors.affiliation: Nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.|NCCR MARVEL, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Carlo A
authors.initials: CA
authors.lastname: Pignedoli
authors.affiliation: Department of Synthetic Chemistry, Max Planck Institute for Polymer Research, 55124 Mainz, Germany.
authors.forename: Xinliang
authors.initials: X
authors.lastname: Feng
authors.affiliation: Department of Synthetic Chemistry, Max Planck Institute for Polymer Research, 55124 Mainz, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen
authors.affiliation: Nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.|Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland.
authors.forename: Roman
authors.identifier: 0000-0002-1553-6487
authors.initials: R
authors.lastname: Fasel
authors.affiliation: Nanotech@surfaces Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Pascal
authors.identifier: 0000-0001-5729-5354
authors.initials: P
authors.lastname: Ruffieux