Noncollinear Coulomb scattering in graphene


Noncollinear Coulomb scattering in graphene

König-Otto, J.; Mittendorff, M.; Winzer, T.; Malic, E.; Knorr, A.; Pashkin, A.; Schneider, H.; Helm, M.; Winnerl, S.

Utilizing the anisotropy of the optical excitation in graphene, we reveal the twofold nature of Coulomb scattering in graphene. The initial nonequilibrium charge carrier distribution in graphene created by linearly polarized light possesses a pronounced anisotropy, which has been observed in our recent experiment [1]. In the present study we perform polarization-dependent pump-probe measurements using a photon energy of 88 meV to suppress efficiently the optical phonon scattering. In this case the relaxation dynamics leading to an isotropic distribution is dominated by noncollinear Coulomb scattering. By varying the pump fluence over a range of several orders of magnitudes we are able to successfully control the efficiency of this process. This reveals a surprising twofold nature of Coulomb scattering in graphene: Whereas collinear Coulomb scattering is known to be a very fast process on the fs timescale, noncollinear scattering is remarkably slow, resulting in a thermalization time of several ps in our experiment. Our experimental findings are complemented by the results of microscopic modelling.
[1] M. Mittendorff et al., Nano Lett. 14, 1504 (2014).

Keywords: graphene; ultrafast dynamics; anisotropy

Related publications

  • Lecture (Conference)
    80. Jahrestagung der DPG und DPG-Frühjahrstagung, 06.-11.03.2016, Regensburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23445
Publ.-Id: 23445