Regensburg 2016 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 40: Focus: Terahertz radiation and magnetism

MA 40.2: Hauptvortrag

Donnerstag, 10. März 2016, 10:00–10:30, H32

Probing and controlling ultrafast magnetism with terahertz electromagnetic pulses — •Tobias Kampfrath — Fritz Haber Institute, Berlin, Germany

Sub-picosecond terahertz (THz) electromagnetic pulses are not only capable of probing and even controlling numerous low-energy excitations such as phonons, excitons and Cooper pairs but they also provide novel access to ultrafast magnetism.

As a first example, we optically launch ultrafast spin transport and study its conversion into charge currents by means of the inverse spin Hall effect [Nature Nanotech. 8, 256 (2013)]. Our approach allows us to monitor ultrafast spin currents, provides a quick and easy estimate of the strength of the spin Hall effect and leads to new and efficient emitters of THz pulses that fully cover the range from 1 to 30 THz without gap [http://arxiv.org/abs/1510.03729]. Second, we probe spin-lattice coupling by selective excitation of optical phonons in the model ferrimagnetic insulator yttrium iron garnet. A magnetization quenching on a time scale as short as 1 ps is found, attesting to a highly efficient equilibration of lattice and spins. We present a new microscopic mechanism of phonon-to-magnon conversion that provides a quantitative explanation of our experimental findings.

The results shown here were obtained in close collaborations with the research groups of L.M. Hayden, M. Kläui, Y. Mokrousov, M. Münzenberg, P.M. Oppeneer, A. Paarmann, I. Radu and D. Turchinovich.