Berlin 2024 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 45: Ultrafast Electron Dynamics at Surfaces and Interfaces IV
O 45.2: Vortrag
Mittwoch, 20. März 2024, 10:45–11:00, MA 041
Influence of twist angle on ultrafast charge transfer in WS2-graphene heterostructures — •Niklas Hofmann1, Leonard Weigl1, Johannes Gradl1, Neeraj Mishra2, 3, Stiven Forti2, Camilla Coletti2, 3, Amir Kleiner4, Daniel Hernangomez-Peres4, Sivan Refaely-Abramson4, and Isabella Gierz1 — 1University of Regensburg, Germany — 2Istituto Italiano di Tecnologia, Pisa, Italy — 3Istituto Italiano di Tecnologia, Genova, Italy — 4Weizmann Institute of Science, Rehovot, Israel
Ultrafast charge separation is crucial for efficiently converting sunlight into electrical energy. This phenomenon commonly occurs in different van der Waals heterostructures [1] where the transfer rates for electrons and holes are determined by the band alignment and interlayer hybridization. Both parameters are expected to be highly sensitive with respect to variations of the twist angle between the layers. This makes the twist angle the decisive tuning parameter for optimizing ultrafast charge transfer processes for various applications. Using time- and angle-resolved photoemission spectroscopy, we investigate the non-equilibrium carrier dynamics in WS2-graphene heterostructures with twist angles of 0° and 30°. We find that, for a twist angle of 0°, hole transfer from WS2 to graphene is significantly faster than electron transfer [2]. For a twist angle of 30°, however, we find no indication for ultrafast charge separation. We interpret our results with the help of ab-initio band structure calculations.
[1] C. Jin et al., Nature Nanotechnology 13, 994 (2018)
[2] S. Aeschlimann et al., Sci. Adv. 6, eaay0761 (2020)
Keywords: Ultrafast charge transfer; Twist angle; 2d heterostructure; time-resolved ARPES