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Philip Hofmann

Ultrafast dynamics of massive dirac fermions in bilayer graphene

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  • Søren Ulstrup
  • Jens Christian Johannsen, École Polytechnique Fédérale de Lausanne, Danmark
  • Federico Cilento, Sincrotrone Trieste, 34149 Trieste, Italy.
  • ,
  • Jill A Miwa
  • Alberto Crepaldi, Sincrotrone Trieste, 34149 Trieste, Italy.
  • ,
  • Michele Zacchigna, IOM-CNR Laboratorio TASC, Area Science Park, 34012 Trieste, Italy.
  • ,
  • Cephise Cacho, Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom.
  • ,
  • Richard Chapman, Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom., Ukendt
  • Emma Springate, Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom.
  • ,
  • Samir Mammadov, Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany., Ukendt
  • Felix Fromm, Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany.
  • ,
  • Christian Raidel, Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany.
  • ,
  • Thomas Seyller, Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany.
  • ,
  • Fulvio Parmigiani, Sincrotrone Trieste, 34149 Trieste, Italy and Department of Physics, University of Trieste, 34127 Trieste, Italy.
  • ,
  • Marco Grioni, École Polytechnique Fédérale de Lausanne
  • ,
  • Phil D C King, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, United Kingdom., Ukendt
  • Philip Hofmann

Bilayer graphene is a highly promising material for electronic and optoelectronic applications since it is supporting massive Dirac fermions with a tunable band gap. However, no consistent picture of the gap's effect on the optical and transport behavior has emerged so far, and it has been proposed that the insulating nature of the gap could be compromised by unavoidable structural defects, by topological in-gap states, or that the electronic structure could be altogether changed by many-body effects. Here, we directly follow the excited carriers in bilayer graphene on a femtosecond time scale, using ultrafast time- and angle-resolved photoemission. We find a behavior consistent with a single-particle band gap. Compared to monolayer graphene, the existence of this band gap leads to an increased carrier lifetime in the minimum of the lowest conduction band. This is in sharp contrast to the second substate of the conduction band, in which the excited electrons decay through fast, phonon-assisted interband transitions.

OriginalsprogEngelsk
TidsskriftPhysical Review Letters
Vol/bind112
Nummer25
Sider (fra-til)257401
ISSN0031-9007
StatusUdgivet - 27 jun. 2014

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