Berlin 2024 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 9: Ultrafast Magnetization Effects II
MA 9.12: Vortrag
Montag, 18. März 2024, 18:15–18:30, H 2013
Exciton-driven phonon dynamics in a magnetic layered semiconductor CrI3 — •Martin Pavelka, Vishal Shokeen, Ruslan Chulkov, Alexander Yaroslavtsev, Johanna Rogvall, David Muradas, Ulrich Noumbe, Mahmoud Abdel-Hafiez, Venkata Kamalakar Mutta, Oscar Grånäs, and Hermann Dürr — Uppsala University, Uppsala, Sweden
CrI3 is a prototype of a new class of magnetic 2D materials displaying ferromagnetic order down to the monolayer limit [1]. Its optical and magneto-optical spectra feature several excitonic dd-transitions characterized by spin-polarized electron and hole pairs with evidence of strong coupling to optical phonons [2].
In this talk, we will describe the ultrafast optical and magneto-optical responses of CrI3. Our two-colour femtosecond spectroscopy allows us to investigate the interplay of exchange interaction and electron-phonon coupling. Following the optical generation of excitons, we observe coherent oscillations in the time-domain. Fourier transformation of the spectra shows two coherent phonon modes, the A1g1 and A1g2 symmetries, at frequencies of 2.4 and 3.9 THz, respectively. Theoretical calculations show that both modes couple to the magnetic order, in agreement with our observations. This finding is contrary to the previous report [2]. The starting phase of these two impulsively excited modes indicates a magnetic contribution to their generation. We also explore the fluence dependence of these phenomena to assess the possible influence of neighbouring excitons.
[1] Nature 546, 270-273 (2017). [2] Nat Commun 13, 4473 (2022).
Keywords: Magnetic two-dimensional materials; Excitons; Coherent phonons