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MA: Fachverband Magnetismus

MA 29: Focus Session: Magnon Polarons – Magnon-Phonon Coupling and Spin Transport (joint session MA/HL)

MA 29.5: Hauptvortrag

Mittwoch, 18. März 2020, 11:15–11:45, HSZ 04

Boltzmann approach to the longitudinal spin Seebeck effect — Piet Brouwer and •Rico Schmidt — Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany

We develop a Boltzmann transport theory of coupled magnon-phonon transport in ferromagnetic insulators. The explicit treatment of the magnon-phonon coupling within the Boltzmann approach allows us to calculate the low-temperature magnetic-field dependence of the spin-Seebeck voltage. We consider both a high-temperature regime, in which magnon and phonon branches are coupled incoherently, and a low-temperature regime, which has strongly coupled magnon-polaron excitations. For the magnetic field dependence of the spin Seebeck voltage in both limits we observe similar features as found by Flebus et al. [Phys. Rev. B 95, 144420 (2017)] for a strongly coupled magnon phonon system that forms magnon-polarons, consistent with experimental findings in yttrium iron garnet by Kikkawa et al. [Phys. Rev. Lett. 117, 207203 (2016)].