Seminars Archive

Ultrafast dynamics in graphene: Coulomb and phonon related effects

Abstract
After a brief introduction into experimental possibilities at the user facility FELBE we will focus on the carrier dynamics in graphene. In particular, the goal is to disentangle the Coulomb and phonon related dynamics. To this end, monitoring the anisotropy of the carrier distribution in k-space in polarization resolved pump-probe experiments is particularly useful [1-3]. It turns out that the decay of the anisotropy is mainly Coulomb related, while the decay of the pump-probe signals is mainly related to carrier cooling via phonons. Furthermore, we discuss the dynamics in Landau quantized graphene [4]. Here, experiments utilizing circularly polarized radiation reveal strong Auger scattering, which is an obstacle regarding Landau level lasing. Here, other materials such as HgCdTe actually may be more promising candidates [5]. Finally, we present very recent experiments on evidence for transient mid-infrared gain in graphene (without magnetic field) found in three-pulse pump-probe experiments. [1] M. Mittendorff et al., Nano Lett. 14, 1504 (2014). [2] J. C.- König-Otto et al., Phys. Rev. Lett. 117, 087401 (2016). [3] A. Seidl et al, Phys. Rev. B 105, 085404 (2022). [4] M. Mittendorff et al., Nature Physics 11, 75 (2015). [5] D. B. But et al, Nature Physics 13, 783 (2019).