Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 34: Plasmonics and nanooptics: Light-matter interaction, spectroscopy III

O 34.2: Talk

Tuesday, March 13, 2018, 14:15–14:30, MA 041

Electron dynamics in gold nanotips — •Andreas Wöste, Thomas Quenzel, Jan Vogelsang, Petra Groß, and Christoph Lienau — Institut für Physik, Carl von Ossietzky Universität, 26129 Oldenburg, Germany

Interaction between electrons and strong electromagnetic fields in solids plays a role in various physical phenomena, for example in optically induced emission of ultrashort electron pulses from metal nanotips. Besides the parameters of the incident laser pulses the electronic configuration of the emitter influences the emission process. On thin films, the electron dynamics are already intensely studied, mostly using two-photon emission pump-probe schemes. More recently, the electron dynamics in metal nanostructures come into focus, due to their potential as laser-triggered emitters in ultrafast electron microscopes. Unfortunately, the two-photon excitation schemes used typically cannot directly be transferred to nanostructures, because the need for wavelengths in the visible or UV regime often damages the samples. Therefore we show a measurement of electron relaxation times on chemicaly etched gold nanotips using multiphoton photoemission in a pump probe scheme with sub 20 fs laser pulses at center wavelengths of 600 nm and 1700 nm. We observe a four-fold increase of electron emission with respect to far delayed pulses, which indicates favored emission out of highly excited, non-thermal states which last for about 100 fs before they decay. The good agreement between our numerical model and the comparable timescale, in comparison with results from measurements on thin films, supports this suggestion.