Tomosato Hioki
In recent years, it was demonstrated that spin angular momentum transfer in magnetic insulators is enhanced or modulated by hybridizing magnons with phonons [1-3]. The hybridization refers to formation of new normal state as a result of interaction between two different excitations. By the hybridization with phonons, some characteristics of phonons are transferred to magnons such as long lifetime and mode degree of freedom.
In this talk, I will discuss the coherent interconversion between magnons and phonons, and demonstration of transfer of mode degree of freedom of phonons to magnons. We developed time-resolved magneto-optical imaging technique by combining conventional magneto-optical imaging and pump-and-probe spectroscopy, which enables us to obtain snapshots of spin-wave propagation dynamics in real space with sub nanoseconds temporal resolutions. In a Bi-doped magnetic garnet, Lu2Bi1Fe3.4Ga1.6O12, we observed coherent temporal oscillation between magnons and phonons as a result of hybridization, where magnons and phonons are coherently interconverted to each other during propagation. It is also found that the magnon-phonon hybridized wave exhibits abnormal reflection at the sample edge owing to the mode degree of freedom of phonons [4]. Since phonons have longitudinal and transverse modes, both modes may not be an eigenstate where translational symmetry is broken down, such as a sample edge. Owing to the mode degree of freedom, the hybridized wave may split into two reflected waves with the same frequency, which is not the case for pure magnon propagation. The experimental demonstration of these dynamics of magnon-phonon hybridized waves will be reported in the talk.
[2] J. Holanda, D. S. Maior, A. Azevedo, and S. M. Rezende, Nat. Phys. 14, 500-506 (2018)
[3] K. An, A. N. Litvinenko, R. Kohno, A. A. Fuad, V. V. Naletov, L. Vila, U. Ebels, G. de Loubens, H. Hurdequint, N. Beaulieu, J. Ben Youssef, N. Vukadinovic, G. E. W. Bauer, A. N. Slavin, V. S. Tiberkevich, and O. Klein, Phys. Rev. B, 101, 060407(R) (2020)
[4] T. Hioki, Y. Hashimoto, E. Saitoh, Commun. Phys. 3, 188 (2020)