Berlin 2024 – scientific programme
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O: Fachverband Oberflächenphysik
O 36: Poster: Ultrafast Electron Dynamics at Surfaces and Interfaces
O 36.26: Poster
Tuesday, March 19, 2024, 18:00–20:00, Poster C
Direct Observation of Ultrafast Electron Dynamics in WS2 via Time- and Angle-Resolved Photoemission Spectroscopy — •Lasse Sternemann, Karl Schiller, Valentin Mischke, Jonah Elias Nitschke, Matija Stupar, Giovanni Zamborlini, and Mirko Cinchetti — Department of Physics, TU Dortmund University, Otto-Hahn-Straße 4, 44227 Dortmund, Germany
Monolayer transition metal dichalcogenides (TMDCs) show great promise for optoelectronic applications and introduce new functionalities, such as valley-selective spin polarization, for information technology. Understanding their electronic band structure and the ultrafast transient dynamics in non-equilibrium states is crucial for harnessing TMDCs’ full potential.
In this study, we visualize the ultrafast electron dynamics in the conduction band of WS2 using time- and angle-resolved photoemission spectroscopy, employing a momentum microscope connected to a femtosecond extreme ultraviolet (XUV) source. We investigate both a commercial bulk WS2 crystal and a self-grown WS2 /Au(111) mono-layer (ML), observing the conduction band’s population dynamics in momentum space in presence of significant bandgap renormalization. Disentangling the population and decay channels of the Σ- and K-valley in the bulk reveals direct and indirect population mechanisms as well as longer lifetimes for the optically dark Σ-valley. The ML displays only the population of the K-valley that exhibits significantly faster dynamics due to coupling to the Au(111).
Keywords: trARPES; TMDC; WS2; Ultrafast Electron Dynamics; HHG