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Paper   IPM / Nano-Sciences / 14742
School of Nano Science
  Title:   Semiconductor-to-Metal Transition and Quasiparticle Renormalization in Doped Graphene Nanoribbons
1.  Boris Senkovskiy
2.  Alexander Fedorov
3.  Danny Haberer
4.  Mani Farjam
5.  Konstantin Simonov
6.  Alexei Preobrajenski
7.  Niels Martensson
8.  Nicolae Atodiresei
9.  Vasile Caciuc
10.  Stefan Blugel
11.  Achim Rosch
12.  Nikolay Verbitskiy
13.  Martin Hell
14.  Daniil Evtushinsky
15.  Raphael German
16.  Tomas Marangoni
17.  Paul van Loosdrecht
18.  Felix Fischer
19.  Alexander Gruneis
  Status:   Published
  Journal: Adv. Electronic Mat.
  Year:  2017
  Pages:   1600490
  Publisher(s):   WILEY-VCH Verlag GmbH & Co
  Supported by:  IPM
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.

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