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O: Fachverband Oberflächenphysik

O 80: Gerhard Ertl Young Investigator Award Competition

O 80.4: Vortrag

Donnerstag, 12. März 2026, 12:00–12:30, TRE/PHYS

Effect of atomic-scale defects on light-matter interaction in transition-metal dichalcogenides — •Vibhuti N. Rai, Junyoung Sim, Florian Faaber, Sergey Trishin, Nils Bogdanoff, Paul Wiechers, Caroline Firschke, Tom S. Seifert, Tobias Kampfrath, Christian Lotze, and Katharina J. Franke — Freie Universität Berlin, Department of Physics, Arnimallee 14,14195 Berlin, Germany

Defects crucially affect the physical properties of (quasi-) two-dimensional materials, such as transition metal dichalcogenides (TMDCs). Here, by using THz scanning tunneling microscopy [1], we excite and detect long-range coherent in-plane shear and out-of-plane breathing modes on the surface of 2H-MoTe₂. We find that atomic-scale intrinsic defects influence their relative excitation efficiency. We attribute this response to local tip-induced band bending [2].

In the monolayer limit, where quantum confinement enhances defect sensitivity, we further show ultrafast charge modulation in defect sites of quasi-freestanding nanopatches of a monolayer MoS₂ on Au(111) driven by THz pulses. These insights into defect-mediated phonon excitation and charge transfer provide a pathway toward future ultrafast electronics.

[1] Cocker et al., Nature Photonics 7, 620-625 (2013)

[2] Rai et al. arXiv:2506.08219v2 (2025)

Keywords: Scanning tunnelling microscopy; Coherentphonon spectroscopy; THz scanning tunnelin microscopy; Atomic scale defects; Transition metal dichalcogenides