SurfaceScience21 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 79: Poster Session VI: Ultrafast electron dynamics at surface and interfaces II

O 79.7: Poster

Mittwoch, 3. März 2021, 13:30–15:30, P

Tracing magnetization dynamics in Fe at the BZ edge by TR-ARPES — •Christian Strüber, Xinwei Zheng, Shabnam Haque, and Martin Weinelt — Freie Universität Berlin, Berlin, Germany

Time- and angle-resolved photoemission spectrocopy (TR-ARPES) allows for the investigation of magnetization dynamics by observing shifts in the electronic band structures and transient changes of the electronic population [1]. The focus of previous experiments often lay on the centre of the Brillouin zone (BZ). However, large parts of the electrons contributing to magnetism are distributed over the whole BZ.

We prepare single-crystalline layers of Fe on W(110) at 300 K and measure TR-ARPES signals at cryogenic temperatures (<100 K). In a pump-probe experiment photoelectrons are excited by ultrashort monochromatic XUV pulses (27.2 eV, 10 kHz, <100 fs) generated via HHG in an argon target. Demagnetization dynamics in the thin-film samples are pumped by intense NIR (770 nm) pulses. We measure the electronic excitation and energy shifts of majority and minority spin bands at the centre of the BZ and for high lateral momentum. We observe different dynamics of bulk and surface resonance states.

Additionally, we observe kinetic energy modulations before the temporal overlap resulting from an interaction with the ponderomotive potential of the pump pulse in front of the Fe sample. We investigate these modulations as a function of kinetic energy, emission angle and pump incidence angle and compare to results in Gd [2].

[1] B.Frietsch et al., Science Advances 6,39(2020)

[2] U. Bovensiepen et al. Physical Review B 79, 045415 (2009)