Valley modulation and topological phase transition in Staggered Kagome Ferromagnets

Abstract

Abstract Owing to its charge-free property, magnon is highly promising to achieve dissipationless transport without Joule heating and thus potentially applicable to energy-efficient devices. Here, we investigate valley magnons and associated valley modulations in a kagome ferromagnetic lattice, with the staggered exchange interaction and Dzyaloshinskii-Moriya interaction. The staggered exchange interaction breaks the spatial inversion symmetry, leading to a valley magnon Hall effect. With nonzero Dzyaloshinskii-Moriya interaction in staggered kagome lattcie, the magnon Hall effect can be observed from only one valley. Moreover, reversing the Dzyaloshinskii-Moriya interaction (D→-D) and exchange of J 1 and J 2 (J 1 ↔ J 2) can also regulate the position of the unequal valleys. With increasing Dzyaloshinskii-Moriya interaction, a series of topological phase transitions appear when two bands come to touch and split at valleys. The valley Hall effect and topological phase transitions observed in kagome magnon lattices can be realized in the thin film of the insulating ferromagnet, such as Lu2V2O7, and will extend the basis for magnonics applications in the future.