Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 63: Poster Wednesday: Ultrafast Processes

O 63.4: Poster

Mittwoch, 3. April 2019, 17:45–20:00, Poster B1

Ultrafast miniaturised pulsed electron gun for time-resolved LEED — •Dennis Epp, Gero Storeck, Max Lukas Kroll, Murat Sivis, and Claus Ropers — IV. Physical Institute, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Solid state surface systems display complex structural and electronic phases, with properties that may drastically differ from the bulk [1]. The coupling between electronic, lattice and spin degrees of freedom can be studied by ultrafast techniques. The structural dynamics associated with transitions between different phases can be studied by the recently developed method of Ultrafast Low-Energy Electron Diffraction (ULEED) [2, 3]. In this method, a miniaturized laser-driven photoelectron source generates ultrashort low-energy electron pulses to probe pump-induced changes to the surface structure in a stroboscopic manner. In recent works, we employed millimetre- and a micrometre-sized photoelectron guns [2, 3]. The reduced outer diameter of both electron sources allows for a small working distance from the sample, minimizing dispersive electron pulse broadening and reducing shadowing on the detector in backscattering. Temporal resolutions down to 16 ps (millimetre-gun) and 1ps (micrometre-gun) are demonstrated. This contribution will describe the fabrication of the electron beam systems, measured beam properties and first applications. Further strategies to facilitate ULEED with sub-picosecond temporal resolution will be discussed. [1] J. M. Kosterlitz. & D. J. Thouless, J. Phys. C 6, 1181*1203 (1973). [2] G. Storeck et al., Structural Dynamics 4, 044024 (2017). [3] S. Vogelgesang, et al., Nature Physics 14,184-190 (2018).

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