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Dresden 2020 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 21: Ultrafast Magnetization II

MA 21.6: Vortrag

Dienstag, 17. März 2020, 10:45–11:00, HSZ 101

Photoinducing coherent Teraherz spin dynamics without spin waves — •M. Terschanski1, S. Dal Conte2, F. Mertens1, G. Springholz3, A. Bonanni3, G. Uhrig4, G. Cerullo2, D. Bossini1, and M. Cinchetti11Experimentelle Physik VI, TU Dortmund, Otto-Hahn-Straße 4, 44227 Dortmund, Germany — 2Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy — 3Institut fuer Halbleiterphysik, University of Linz, Altenberger Straße 69, 4040 Linz, Austria — 4Theoretische Physik I, TU Dortmund, Otto-Hahn-Straße 4, 44227 Dortmund, Germany

Ultrafast coherent spin dynamics is generally induced generating magnon modes at their specific frequencies and according to their selection rules. Here we present a different approach: First, absorption measurements of hexagonal bulk α-MnTe revealed a coupling between the magnetic order and the band gap energy Eg below the Neél temperature (TN = 307 K): a contribution to Eg proportional to the sublattice magnetization M was observed. Second, in a pump-probe experiment a 5 THz coherent phonon was induced, modulating the band-gap energy and thus the reflectivity of MnTe. Finally, we perform time-resolved magneto-optical measurements to assess whether the photo-induced band-gap dynamics affect the spin system. The temperature dependence of the magneto-optical signal proves that a 5 THz oscillation of the sublattice magnetization is driven by the band-gap dynamics. We thus disclose the excitation of coherent THz spin dynamics without the generation of magnons.

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