[2D12-21] Surface Science (SS1) Physical Property

4:00 PM - 4:15 PM JST(7:00 AM - 7:15 AM UTC)

[2D17] Probing Floquet-Bloch state using quantum-beat spectroscopy

Yu-Chan Tai^1,2, Chih-Wei Luo², Noriaki Takagi³, Hiroshi Ishida⁴, Chun-Liang Lin², *ryuichi arafune¹ (1. Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Sciecne (Japan), 2. Departmentt of Electrophysics, National Yang Ming Chiao Tung University (Taiwan), 3. Graduate School of Human and Environmental Studies, Kyoto University (Japan), 4. College of Humanities and Sciences, Nihon University (Japan))

We show that laser-excited coherent phonons drive Floquet-Bloch states. Using time-resolved multiphoton photoemission combined with quantum beat spectroscopy on graphene-covered Ir(111), we track the coherent electronic dynamics of the image-potential states dressed by coherent phonons. The beat signal indicates the presence of sideband structure with the coherent-phonon frequency as its fundamental period, consistent with Floquet theory. Furthermore, an independent oscillation in intensity at the same frequency was observed, confirming excitation of the coherent phonon mode. Compared with conventional light-driven Floquet-Bloch states, the observed phonon-driven Floquet-Bloch states persist for one to two orders of magnitude longer. These results establish a time-domain route to identifying phonon-driven Floquet-Bloch states and reveal their formation on ultrafast timescales.

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