Regensburg 2022 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 7: New Methods and Developments 1: Scanning Probe Techniques 1 (joint session O/KFM)
O 7.6: Vortrag
Montag, 5. September 2022, 12:00–12:15, S053
Coherent phonon spectroscopy on the nanoscale — Shuyi Liu1, Adnan Hammud1, Ikutaro Hamada2, Martin Wolf1, •Melanie Müller1, and Takashi Kumagai3 — 1Fritz-Haber-Institut, Berlin, Germany — 2College of Materials Science and Engineering, Hunan, China — 3Institute for Molecular Science, Okazaki, Japan
Coherent phonon (CP) spectroscopy is a powerful tool to monitor ultrafast lattice dynamics under nonequilibrium conditions, providing insight into microscopic interactions that dictate macroscopic material properties. In imperfect crystals, the excitation and relaxation of CPs will be susceptible to the nanoscale environment, calling for real-space observation of ultrafast lattice dynamics. We demonstrate nanoscale coherent phonon spectroscopy by means of ultrafast laser-induced scanning tunneling microscopy (STM) in a plasmonic junction. Comparison of the CP spectra with tip-enhanced Raman spectroscopy allows us to identify the involved phonon modes. In contrast to the Raman spectra, the relative CP intensities exhibit strong nanoscale spatial variations, which correlate with changes in the local density of states recorded via scanning tunneling spectroscopy. Our work introduces a new approach to study the ultrafast structural response at solid surfaces using optical STM.