title: Signature of the Dirac cone in the properties of linear oligoacenes.
abstract: Organic electronics offers prospects of functionality for science, industry and medicine that are new as compared with silicon technology and available at a very low material cost. Among the plethora of organic molecules available for materials design, polymers and oligomers are very promising, for example, because of their mechanical flexibility. They consist of repeated basic units, such as benzene rings, and the number of these units N determines their excitation gap, a property that is often used in proposals of organic photovoltaics. Here, we show that contrary to a widely held belief the magnitudes of excitation gaps do not always decay monotonously with N, but can oscillate due to the presence of a 'Dirac cone' in the band structure. With an eye on the more fundamental question how a molecular wire becomes metallic with increasing length, our research suggests that the process can exhibit incommensurate oscillations.
authors.affiliation: Institut für Nanotechnologie, Karlsruhe Institute of Technology (KIT), PO Box 3640, 76021 Karlsruhe, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Korytár
authors.affiliation: 1] Institut für Nanotechnologie, Karlsruhe Institute of Technology (KIT), PO Box 3640, 76021 Karlsruhe, Germany [2] Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 CNRS-UdS, 23, Rue du Loess, BP 43, 67034 Strasbourg, France.
authors.forename: Dimitra
authors.initials: D
authors.lastname: Xenioti
authors.affiliation: 1] Institut für Nanotechnologie, Karlsruhe Institute of Technology (KIT), PO Box 3640, 76021 Karlsruhe, Germany [2] DFG Center for Functional Nanostructures, Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Str. 1a, 76131 Karlsruhe, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Schmitteckert
authors.affiliation: Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 CNRS-UdS, 23, Rue du Loess, BP 43, 67034 Strasbourg, France.
authors.forename: Mébarek
authors.initials: M
authors.lastname: Alouani
authors.affiliation: 1] Institut für Nanotechnologie, Karlsruhe Institute of Technology (KIT), PO Box 3640, 76021 Karlsruhe, Germany [2] DFG Center for Functional Nanostructures, Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Str. 1a, 76131 Karlsruhe, Germany [3] Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Str. 1, 76128 Karlsruhe, Germany.
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Evers