Berlin 2024 – scientific programme

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O: Fachverband Oberflächenphysik

O 36: Poster: Ultrafast Electron Dynamics at Surfaces and Interfaces

O 36.16: Poster

Tuesday, March 19, 2024, 18:00–20:00, Poster C

Few electron correlations from nanometric needle tips triggered by femtosecond laser pulses — •Felix Lopez Hoffmann, Jonas Heimerl, Stefan Meier, and Peter Hommelhoff — Department Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen

Metal needle tips are a standard source of free electrons for electron microscopes. When many electrons are emitted from such tips, space charge effects due to Coulomb repulsion appear as intuitively expected [1]. Here we demonstrate that already two electrons repel each other if confined tightly in space and time. In specific, we use femtosecond laser pulses to trigger multiphoton photoemission from metallic needle tips with a few nanometer in radius. The emitted electron pairs show an energy anti-correlation with a visibility of 56%, a mean energy splitting of 3.3 eV and a correlation decay time of 82 fs [2]. Similar results have been obtained in a TEM [3]. By energy filtering the emitted beam the number distribution of electrons per laser pulse can be tuned from Poissonian to sub/super-Poissonian statistics. Sub-Poissonian emission, in our case with a second order correlation g(2) as low as 0.34, allows for shot-noise reduced imaging. Using such Coulomb-induced energy splitting, also heralding of electrons becomes possible. Furthermore, we show first results on spatial correlations stemming from transverse momentum exchange.

[1] Kuwahara et al., Appl. Phys. Lett. 109(1), 013108 (2016)

[2] Meier et al., Nat. Phys. 1-8 (2023)

[3] Haindl et al., Nat. Phys. 19, 1410-1417 (2023)

Keywords: electron source; correlation; sub-poissonian; photoemission