Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 79: Ultrafast Electron Dynamics III

O 79.4: Talk

Thursday, March 20, 2025, 11:15–11:30, H2

Quenching Strong-Field Recollisions at Nanotapers with Strong Bias Fields — •Rasmus Lampe, Germann Hergert, and Christoph Lienau — Institut für Physik, Carl-von-Ossietzky Universität, 26129 Oldenburg, Germany

Recollisions of intensively accelerated electrons with the parent are a well-known effect in strong-field photoemission of electrons, leading to photoemission spectra showing a recollision plateau with a cut-off energy of ten times the ponderomotive energy. It has recently been demonstrated that such a recollision plateau also arises in multiphoton photoemission from metallic nanostructures, showing that recollisions are much more fundamental to photoemission than anticipated [1].

We analyze electron recollisions from strongly biased tungsten nanotapers illuminated by few-cycle near-infrared laser pulses. We demonstrate significant changes in the photoelectron spectra in the strong-field regime by applying static electric fields on the order of the optical near-field driving the photoemission. A continuous transition of a horizontal recollision plateau into triangularly shaped spectra is observed.

Stronger static fields increase the acceleration of the electrons away from the apex, such that the ponderomotive acceleration by the near-field is not sufficient to drive the electrons back to the surface, ultimately suppressing recollisions. This enables the control of the electron motion with bias fields, which has an immediate importance for ultrafast low-energy electron microscopy allowing to maintain few fs time resolution of the electron beam over mesoscopic distances.

[1] B. Bánhegyi et al., Phys. Rev. Lett. 133, 033801 (2024)

Keywords: Electron point source; Strong-field photoemission; Electron rescattering; Ultrafast electron emission; Biased metal nanotapers