Femtosecond formation dynamics of the spin Seebeck effect revealed by terahertz spectroscopy

Tom S. Seifert, Samridh Jaiswal, Joseph Barker, Sebastian T. Weber, Ilya Razdolski, Joel Cramer, Oliver Gueckstock, Sebastian F. Maehrlein, Lukas Nadvornik, Shun Watanabe, Chiara Ciccarelli, Alexey Melnikov, Gerhard Jakob, Markus Münzenberg, Sebastian T.B. Goennenwein, Georg Woltersdorf, Baerbel Rethfeld, Piet W. Brouwer, Martin Wolf, Mathias KläuiTobias Kampfrath

Research output: Contribution to journalArticlepeer-review

48 Citations (Scopus)

Abstract

Understanding the transfer of spin angular momentum is essential in modern magnetism research. A model case is the generation of magnons in magnetic insulators by heating an adjacent metal film. Here, we reveal the initial steps of this spin Seebeck effect with <27 fs time resolution using terahertz spectroscopy on bilayers of ferrimagnetic yttrium iron garnet and platinum. Upon exciting the metal with an infrared laser pulse, a spin Seebeck current js arises on the same ~100 fs time scale on which the metal electrons thermalize. This observation highlights that efficient spin transfer critically relies on carrier multiplication and is driven by conduction electrons scattering off the metal–insulator interface. Analytical modeling shows that the electrons’ dynamics are almost instantaneously imprinted onto js because their spins have a correlation time of only ~4 fs and deflect the ferrimagnetic moments without inertia. Applications in material characterization, interface probing, spin-noise spectroscopy and terahertz spin pumping emerge.

Original languageEnglish
Article number2899
JournalNature communications
Volume9
Issue number1
DOIs
Publication statusPublished - 2018 Dec 1

ASJC Scopus subject areas

  • Chemistry(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Physics and Astronomy(all)

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