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O: Fachverband Oberflächenphysik

O 17: Mini-Symposium: Frontiers of electronic-structure theory: Focus on electron-phonon interactions I

O 17.3: Invited Talk

Monday, March 1, 2021, 14:30–15:00, R3

Out-of-equilibrium lattice dynamics in two-dimensional materials — •Fabio Caruso — Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel

The coupling between electronic and vibrational degrees of freedom influences profoundly the ultrafast dynamics of electrons [1] and phonons [2]. We conducted first-principles calculations of the coupled electron-phonon dynamics to investigate the characteristic fingerprints of crystal-lattice vibrations in systems driven out of equilibrium by the interaction with ultra-short light pulses. The relaxation of photo-excited carriers via phonon emission exhibits a striking selectivity in momentum space, and it underpins the emergence of a non-thermal vibrational state of the lattice. These vibrational excited states are characterized by a highly anisotropic population of different phonons and persist for up to 10 ps, until thermal equilibrium is re-established by phonon-phonon scattering. For the prototypical layered semiconductors black phosphorus and MoS2, these findings are corroborated by femto-second electron diffuse scattering (FEDS) experiments [3]. The control of non-thermal vibrational states may provide unexplored opportunities to selectively enhance the phonon population and, thereby, transiently tailor electron-phonon interactions over picosecond time scales.

[1] Caruso, Novko, Draxl, Phys. Rev. B 101, 035128 (2020). [2] Novko, Caruso, Draxl, Cappelluti, Phys. Rev. Lett. 124, 077001 (2020). [3] Seiler, Zahn, Zacharias, Hildebrandt, Vasileiadis, Windsor, Qi, Carbogno, Draxl, Caruso, Ernstorfer, arXiv:2006.12873 (2020).