Regensburg 2025 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 10: Focus Session Ultrafast Electron Microscopy at the Space-Time Limit II

O 10.4: Vortrag

Montag, 17. März 2025, 16:00–16:15, H2

Ultra-Nonlinear Subcycle Photoemission of Few-Electron States from Sharp Gold Nanotapers — •Germann Hergert, Rasmus Lampe, Andreas Wöste, and Christoph Lienau — Institut für Physik, Carl-von-Ossietzky Universität, 26129 Oldenburg, Germany

Generating attosecond electron pulse trains by coherent modulation of swift electrons enabled attosecond resolution in ultrafast transmission electron microscopy [1,2]. The possibility to transfer photon statistics to the electron number statistics in multiphoton photoemission (MPP) from nanotapers [3], opens up a window to increase photoemission nonlinearities of few-electron states and generating subcycle electron pulses. This provides an alternative road to reach subcycle resolution in electron microscopy.

Here, we present MPP of few-electron wavepackets triggered by near-infrared pulses from gold nanotapers, demonstrating 20th-order nonlinearities for electron triplets. Event-based interferometric autocorrelations of the photoemission yield are quenched to single-peak traces with 0.8 fs duration. We observe a modulation of the electron yield by the carrier-envelope phase, indicating the emission of subcycle isolated electron beams, with prospects to improve the temporal resolution in ultrafast point-projection electron microscopy.

[1] D. Nabben, Nature, 619, 63 (2023)

[2] J. Gaida, Nat. Photon., 18, 509 (2024)

[3] J. Heimerl, Nat. Phys., 20, 945 (2024)

[4] G. Hergert, Nano Lett., 24, 11067 (2024)

Keywords: Ultrafast photoemission; Point-projection electron microscopy; Electron number states; Low energy electrons; Optical near-fields