Regensburg 2025 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 5: Scanning Probe Microscopy: Light-Matter Interactions at the Atomic Scale I
O 5.10: Vortrag
Montag, 17. März 2025, 12:45–13:00, H6
Tracking phonon-induced electronic dynamics on atomic scale with ultrafast tunnelling spectroscopy — Carmen Roelcke, Lukas Kastner, Maximilian Graml, Jan Wilhelm, Jascha Repp, Rupert Huber, and •Yaroslav Gerasimenko — Department of Physics and Regensburg Centre for Ultrafast Nanoscopy, University of Regensburg, 93040 Regensburg, Germany
Atomic-defect-based quantum systems in monolayers and moiré heterostructures of 2D materials have attracted huge interest for their qubit and single-photon emission functionalities, but directly observing the interplay of their electronic structure with elementary excitations remained a long-held dream.
We directly resolve in space, time and energy how spin-orbit-split bound states of an individual Se vacancy – an atomic single-photon emitter – evolve under coherent lattice vibrations in moiré-distorted WSe2 using lightwave-driven scanning tunnelling spectroscopy [1]. We selectively launch a drum phonon mode with a THz pulse coupled to the tip and take ultrafast snapshots of electronic spectrum on atomic scales faster than a vibration period. Such ultrafast tunnelling spectra reaching ∼300 fs temporal resolution reveal transient energy shifts of the lower vacancy state by up to 40 meV, depending on the amplitude and phase of the coherent lattice vibration. We discuss how THz fields can couple via the Coulomb interactions to the drum mode, and how the interplay of Se-W bonds distortion and image charge renormalization affect the energy levels of the vacancy.
[1] C. Roelcke et al., Nat. Photon. 18, 595-602 (2024)
Keywords: ultrafast; STS; defect; monolayer; quantum