Localized Excitation in the Backward Volume Mode based 1D Magnonic Crystals

Topology in the 1D crystals has been attracting much attention due to the rich topological properties in simple structures. However, there are lack of discussions of the band topology in the 1D solid state systems with the negative dispersion relation. In this presentation, we discuss the topological characteristics of a yttrium iron garnet based 1D semi-infinite heterostructure magnonic crystal in the bias magnetic field parallel to the propagation direction known as the backward volume mode spin wave configuration. We solved the linearized Landau-Lifshitz equation with the plane-wave method to calculate the band structures, wave functions and the Zak(1D Berry) phases. Furthermore, we utilized a micromagnetic simulation software; MUMAX3[1] to simulate spin wave excitation in the finite structures. As a result, we demonstrate appearance of the localized states in the forbidden region below the first band which has not been reported in other 1D solid state systems. In addition, we show that the edge mode still satisfies the 1D bulk-boundary correspondence described by Zak[2]. We anticipate that our new finding provides further understanding of the topology in 1D solid state systems.

[1] A. Vansteenkiste, et al., AIP Adv. 4, 107133 (2014).

[2] J. Zak, Phys. Rev. B. 32, 2218 (1985).