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

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.

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Item Type:	Article
Authors/Creators:	Seifert, TS Jaiswal, S Barker, J https://orcid.org/0000-0003-4843-5516 Weber, ST Razdolski, I Cramer, J Gueckstock, O Maehrlein, SF Nadvornik, L Watanabe, S Ciccarelli, C Melnikov, A Jakob, G Münzenberg, M Goennenwein, STB Woltersdorf, G Rethfeld, B Brouwer, PW Wolf, M Kläui, M Kampfrath, T
Copyright, Publisher and Additional Information:	© 2018, The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.
Dates:	Accepted: 13 June 2018 Published (online): 24 July 2018 Published: 24 July 2018
Institution:	The University of Leeds
Academic Units:	The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Condensed Matter (Leeds)
Depositing User:	Symplectic Publications
Date Deposited:	08 Oct 2018 14:09
Last Modified:	08 Oct 2018 14:09
Status:	Published
Publisher:	Springer Nature
Identification Number:	10.1038/s41467-018-05135-2
Open Archives Initiative ID (OAI ID):	oai:eprints.whiterose.ac.uk:136765

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

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