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HL: Fachverband Halbleiterphysik

HL 45: Organic electronics and photovoltaics: OPV II (CPP with HL/TT)

HL 45.2: Vortrag

Mittwoch, 18. März 2015, 09:45–10:00, C 130

Signature of the Dirac cone in the excitation gaps of linear oligoacenes — •Richard Korytár — Institut für Nanotechnologie, Karlsruher Institut für Technologie, Herrmann-von-Helmholtzplatz 1, 76344 Eggenstein-Leopoldshafen

Linear oligoacenes (linearly fused benzene rings) are one of the prototypical examples of quantum wires and the simplest realization of the so called nano-graphene. We show that contrary to a widely held belief, the excitation gaps of oligoacenes can display oscillations of period 11 (rings) as a function of the molecule's length. By inspection of the polyacene electronic band-structure, we show that the incommensurate oscillations are caused by the presence of an accidental degeneracy at the Fermi level, reminiscent to the Dirac cone of graphene. Our predictions are supported by calculations based on density functional theory. We clarify the role of interactions by studying a parameterized Hubbard model with density matrix renormalization group. Our findings may have implications for organic electronics and research of materials for energy conversion.