Perspectives and Challenges of Lightwave ARPES

日時　2025年1月27日　（月）　14：00-15：00
場所　広島大学放射光科学研究所　2階　セミナー室
講師　Ulrich Höfer
(Department of Physics, Philipps University of Marburg, Germany and Regensburg Center for Ultrafast Nanoscopy (RUN), Regensburg, Germany )

Lightwave ARPES, a recent development of time- and angle-resolved photoemission (APRES), makes it possible to explore light-matter interaction in the strong field regime with subcycle time resolution. Our first experiment employed electric fields of a few kV/cm from a THz wave to induce electrical surface currents [1]. Recently, we demonstrated subcycle time-resolution at mid-infrared frequencies of 25-40 THz and electric fields in the MV/cm range. Under these conditions, Floquet-Bloch sidebands of the Dirac state build up and our experiments reveals that this occurs already in the second optical cycle of the driving field [2]. A wealth of new opportunities for lightwave ARPES arise from laser high-harmonics for photo¬emission. In combination with orbital tomography [3] it should, e.g., become possible to take slow-motion movies of molecular orbitals while chemical bonds are formed or broken. I will briefly discuss challenges that need to be overcome in order to perform time-resolved photoemission experiments under such extreme conditions and discuss the perspec-tives to achieve attosecond time resolution in lightwave APRES.

[1] J. Reimann et al., “Subcycle observation of lightwave-driven Dirac currents”, Nature 562, 396 (2018)
[2] S. Ito et al., “Ultrafast birth, rise, and collapse of a Floquet-Bloch band structure”, Nature 616, 696 (2023)
[3] R. Wallauer et al., “Tracing orbital images on ultrafast time scales”, Science 371, 1056 (2021)

問合せ先　黒田健太(先進理工系科学研究科)、出田真一郎(放射光科学研究所）