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Author: Strüber, Christian × DDC: 600 ×

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    Element-specific magnetization dynamics of complex magnetic systems probed by ultrafast magneto-optical spectroscopy
    (Basel : MDPI, 2020) Korff Schmising, Clemens von; Willems, Felix; Sharma, Sangeeta; Yao, Kelvin; Borchert, Martin; Hennecke, Martin; Schick, Daniel; Radu, Ilie; Strüber, Christian; Engel, Dieter W.; Shokeen, Vishal; Buck, Jens; Bagschik, Kai; Viefhaus, Jens; Hartmann, Gregor; Manschwetus, Bastian; Grunewald, Soeren; Düsterer, Stefan; Jal, Emmanuelle; Vodungbo, Boris; Lüning, Jan; Eisebitt, Stefan
    The vision to manipulate and control magnetism with light is driven on the one hand by fundamental questions of direct and indirect photon-spin interactions, and on the other hand by the necessity to cope with ever growing data volumes, requiring radically new approaches on how to write, read and process information. Here, we present two complementary experimental geometries to access the element-specific magnetization dynamics of complex magnetic systems via ultrafast magneto-optical spectroscopy in the extreme ultraviolet spectral range. First, we employ linearly polarized radiation of a free electron laser facility to demonstrate decoupled dynamics of the two sublattices of an FeGd alloy, a prerequisite for all-optical magnetization switching. Second, we use circularly polarized radiation generated in a laboratory-based high harmonic generation setup to show optical inter-site spin transfer in a CoPt alloy, a mechanism which only very recently has been predicted to mediate ultrafast metamagnetic phase transitions. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
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    Strong-field ionization of clusters using two-cycle pulses at 1.8 μm
    ([London] : Macmillan Publishers Limited, part of Springer Nature, 2016) Schütte, Bernd; Ye, Peng; Patchkovskii, Serguei; Austin, Dane R.; Brahms, Christian; Strüber, Christian; Witting, Tobias; Ivanov, Misha Yu; Tisch, John W. G.; Marangos, Jon P.
    The interaction of intense laser pulses with nanoscale particles leads to the production of high-energy electrons, ions, neutral atoms, neutrons and photons. Up to now, investigations have focused on near-infrared to X-ray laser pulses consisting of many optical cycles. Here we study strong-field ionization of rare-gas clusters (103 to 105 atoms) using two-cycle 1.8 μm laser pulses to access a new interaction regime in the limit where the electron dynamics are dominated by the laser field and the cluster atoms do not have time to move significantly. The emission of fast electrons with kinetic energies exceeding 3 keV is observed using laser pulses with a wavelength of 1.8 μm and an intensity of 1 × 1015 W/cm2, whereas only electrons below 500 eV are observed at 800 nm using a similar intensity and pulse duration. Fast electrons are preferentially emitted along the laser polarization direction, showing that they are driven out from the cluster by the laser field. In addition to direct electron emission, an electron rescattering plateau is observed. Scaling to even longer wavelengths is expected to result in a highly directional current of energetic electrons on a few-femtosecond timescale.