1 Department of Physics and Astronomy, Science and Technology, Aarhus University2 Interdisciplinary Nanoscience Center - INANO-Fysik, Ny Munkegade, Interdisciplinary Nanoscience Center, Science and Technology, Aarhus University3 École Polytechnique Fédérale de Lausanne4 Sinctrotrone Trieste5 Sincrotrone Trieste6 IOM-CNR Laboratorio TASC7 STFC Rutherford Appleton Laboratory8 Technische Universität Chemnitz9 Sincrotrone Trieste & University of Trieste10 Department of Physics and Astronomy, Science and Technology, Aarhus University
The ultrafast dynamics of excited carriers in graphene is closely linked to the Dirac spectrum and plays a central role for many electronic and optoelectronic applications. Harvesting energy from excited electron-hole pairs, for instance, is only possible if these pairs can be separated before they lose energy to vibrations, merely heating the lattice. Until now, the hot carrier dynamics in graphene could only be accessed indirectly. Here, we present a dynamical view on the Dirac cone by time- and angle-resolved photoemission spectroscopy. This allows us to show the quasi-instant thermalization of the electron gas to a temperature of 2000 K, to determine the time-resolved carrier density, and to disentangle the subsequent decay into excitations of optical phonons and acoustic phonons (directly and via supercollisions).