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Schematic illustration of the electronic bandstructure of graphene (only the conduction band is shown). An excited electron can either scatter along or across the Dirac cone. The latter processes change the angle between the initial and the final states () giving rise to an isotropic carrier distribution.
Carrier occupation is shown as a function of the momentum k and the angle around the Dirac point at different times . The initially highly anisotropic and centered non-equilibrium carrier occupation becomes redistributed due to the efficient many-particle relaxation dynamics. The white arrows indicate the scattering along and across the Dirac cone, which accounts for the isotropic carrier distribution already after 50 fs.
Contour plot of the carrier occupation as a function of the momentum k and the angle comparing the relaxation dynamics taking into account only (a) carrier-carrier and (b) carrier-phonon scattering channels. The figure illustrates the crucial importance of phonons for reaching an isotropic carrier distribution within the first 50 fs.
The same as in Fig. 3, however, comparing the carrier dynamics taking into account only the scattering with (a) and (b) phonons. It displays the relaxation in steps of the corresponding constant optical phonon energy. phonons preferably scatter across and along the Dirac cone.
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