Regensburg 2022 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 9: Ultrafast Electron Dynamics at Surfaces and Interfaces 2

O 9.11: Vortrag

Montag, 5. September 2022, 17:30–17:45, H3

SHG imaging microscopy of ultrafast charge-transfer dynamics in twisted TMDC heterostructures — •Marleen Axt, Jonas E. Zimmermann, Gerson Mette, and Ulrich Höfer — Fachbereich Physik, Philipps Universität Marburg, Germany

Two-dimensional heterostructures of transition metal dichalcogenides (TMDC) represent very well-defined model systems of van-der-Waals interfaces. Many material combinations feature a type-II band alignment, which can separate photoexcited electrons and holes into different layers through ultrafast charge transfer leading to the formation of so-called interlayer excitons or interface excitons.

We investigate the ultrafast charge-transfer dynamics in TMDC heterostructures as a function of the stacking angle using time-resolved second-harmonic generation (SHG) imaging microscopy. This experimental technique combines the advantages of SHG with high temporal and spatial resolution. For differently twisted MoS₂/WSe₂ heterostructures the electron transfer from WSe₂ to MoS₂ after resonant excitation (1.70 eV) was found to depend considerably on the twist angle. The transfer time is reduced from 85 fs down to 12 fs when going from a larger rotational mismatch (16^∘) towards 2H-stacking (52^∘).