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Semiconductor-to-Metal Transition and Quasiparticle Renormalization in Doped Graphene Nanoribbons

Authors/others:Senkovskiy, Boris V. (Universität zu Köln) Fedorov, Alexander V. (Universität zu Köln) Haberer, Danny (University of California, Berkeley) Farjam, Mani (Institute for Research in Fundamental Sciences (IPM)) Simonov, Konstantin A. (Uppsala University) Preobrajenski, Alexei B. (Lund University) Mårtensson, Niels (Uppsala University) Atodiresei, Nicolae (Forschungszentrum Jülich) Caciuc, Vasile (Forschungszentrum Jülich) Blügel, Stefan (Forschungszentrum Jülich) Rosch, Achim (Universität zu Köln) Verbitskiy, Nikolay I. (Universität zu Köln) Hell, Martin (Universität zu Köln) Evtushinsky, Daniil V. (Helmholtz-Zentrum Berlin für Materialien und Energie) German, Raphael (Universität zu Köln) Marangoni, Tomas (University of California, Berkeley) van Loosdrecht, Paul H.M. (Universität zu Köln) Fischer, Felix R. (University of California, Berkeley) Grüneis, Alexander (Universität zu Köln)

A semiconductor-to-metal transition in N = 7 armchair graphene nanoribbons causes drastic changes in its electron and phonon system. By using angle-resolved photoemission spectroscopy of lithium-doped graphene nanoribbons, a quasiparticle band gap renormalization from 2.4 to 2.1 eV is observed. Reaching high doping levels (0.05 electrons per atom), it is found that the effective mass of the conduction band carriers increases to a value equal to the free electron mass. This giant increase in the effective mass by doping is a means to enhance the density of states at the Fermi level which can have palpable impact on the transport and optical properties. Electron doping also reduces the Raman intensity by one order of magnitude, and results in relatively small (4 cm−1) hardening of the G phonon and softening of the D phonon. This suggests the importance of both lattice expansion and dynamic effects. The present work highlights that doping of a semiconducting 1D system is strikingly different from its 2D or 3D counterparts and introduces doped graphene nanoribbons as a new tunable quantum material with high potential for basic research and applications.

Date of publication:1.4.2017
Journal title:Advanced Electronic Materials
Digital Object Identifier (DOI):https://doi.org/10.1002/aelm.201600490
Publication Type:Article
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