Dresden 2026 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 43: Scanning probe microscopy: light matter interaction at atomic scales – Poster

O 43.9: Poster

Dienstag, 10. März 2026, 14:00–16:00, P2

Excitation of phonons by THz near fields in a quasi-suspended nanoscopic monolayer of MoS2 — •Junyoung Sim, Vibhuti Rai, Caroline Firschke, Christian Lotze, and Katharina J. Franke — Freie Universtiät Berlin, Department of Physics, Arnimallee 14, 14195 Berlin, Germany

Phonons play a central role in describing fundamental physical properties of materials, such as heat capacity and resistivity, and also govern many-body phenomena such as superconductivity and charge-density waves. To resolve ultrafast lattice vibrations at the atomic scale, terahertz scanning tunneling microscopy (THz-STM) has provided important groundworks, where such vibrations are influenced by the presence of atomic-scale defects [1, 2].

In this work, we investigate the phonon dynamics in a monolayer molybdenum disulfide (MoS2) grown on a Au(111) surface. We focus on nanoscopic regions, where the MoS2 layer is suspended and the electronic structure is minimally hybridized with the substrate [3]. We observe an oscillatory behavior in the THz-STM pump-probe spectra on these suspended regions, which we assign to a coherent vibrational mode excited and measured by the tip-enhanced THz near field. To elucidate the excitation mechanism of the phonon modes, we vary the pump/probe field and investigate the influence of defects within the suspended area.

[1] Roelcke et al., Nature Photonics. 18, 595-602 (2024)

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

[3] Krane et al., Nano Lett. 2016, 16, 8, 5163-5168 (2016)

Keywords: THz-STM