SKM 2021 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 11: 2D semiconductors and van der Waals heterostructures II (joint session HL/DS)
DS 11.5: Vortrag
Freitag, 1. Oktober 2021, 14:30–14:45, H4
Spatio-temporal dynamics of phonon sidebands in 2D materials — •Roberto Rosati1, Koloman Wagner2, Samuel Brem1, Raül Perea-Causín3, Jonas D. Ziegler2, Jonas Zipfel2, Takashi Taniguchi4, Kenji Watanabe4, Alexey Chernikov2,5, and Ermin Malic1,3 — 1Philipps University of Marburg — 2University of Regensburg — 3Chalmers University of Technology — 4National Institute for Materials Science — 5Dresden University of Technology
The semiconducting monolayers of transition metal dichalcogenides (TMDs) display a complex manifold of bright and dark exciton states, the latter giving rise to sharp phonon sidebands (PSB) in low-temperature photoluminescence. In this joint theory-experiment study we theoretically predict and experimentally demonstrate time-resolved low-temperature PSB, thus gaining direct access to the evolution of dark excitons in time, energy and space [1,2]. In an excellent theory-experiment agreement we reveal a spectral red-shift of phonon sidebands on a time scale of tens of picoseconds due to phonon-driven thermalization of initially-formed hot momentum-dark excitons [1]. After confined optical excitation, such hot-exciton distribution gives rise to a transient exciton diffusion one order of magnitude faster than the conventional diffusion observed at later times [2]. The obtained insights are applicable to other 2D materials with multiple exciton valleys.
[1] Rosati, R. et al. ACS Photonics 7, 2756 (2020).
[2] Rosati, R. et al. arXiv:2105.10232 (2021).