Regensburg 2022 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 9: Ultrafast Electron Dynamics at Surfaces and Interfaces 2
O 9.13: Vortrag
Montag, 5. September 2022, 18:00–18:15, H3
Subcycle lightwave-ARPES in the strong-field regime — Suguru Ito1, Manuel Meierhofer2, Josef Freudenstein2, Dmytro Afanasiev2, •Jens Güdde1, Rupert Huber2, and Ulrich Höfer1 — 1Fachbereich Physik, Philipps-Universität Marburg, Germany — 2Fakultät für Physik, Universität Regensburg, Germany
Angle-resolved photoemission spectroscopy (ARPES) combined with THz excitation enables the investigation of lightwave-driven Dirac currents in the surface state of topological insulators with sub-cycle time resolution [1]. At low THz frequencies and moderate effective field strengths of a few kV/cm at the surface, we have shown that the current dynamics is dominated by intraband acceleration of the electrons within the surface band of Bi2Te3.
Here, we will show how such experiments can be extended to the strong-field regime at driving frequencies of 25-40 THz. This is challenged by strong energy and momentum streaking of the photoelectrons after photoemission as well as the requirement of ultrashort pulses for photoemission which also introduce considerable energy broadening of the ARPES spectra. We will discuss how these challenges can be successfully overcome in order to enable lightwave-ARPES at field strength of ∼1 MV/cm despite surface screening. This paves the way for visualizing strong-field phenomena such as high-harmonic generation (HHG) [2] and the emergence of Floquet-Bloch states directly in the band structure on a sub-optical-cycle time scale.
[1] J. Reimann et al., Nature 562, 396 (2018).
[2] C. P. Schmid et al., Nature 593, 385 (2021).