Valley modulation and topological phase transition in staggered kagome ferromagnets

Abstract Owing to their charge-free property, magnons are highly promising for achieving dissipationless transport without Joule heating, and are thus potentially applicable to energy-efficient devices. Here, we investigate valley magnons and associated valley modulations in a kagome ferromagnetic lattice with 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 a staggered kagome lattice, the magnon Hall effect can be observed from only one valley. Moreover, reversing the Dzyaloshinskii–Moriya interaction ( D → − D ) and exchanging 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 the valleys. The valley Hall effect and topological phase transitions observed in kagome magnon lattices can be realized in thin films of insulating ferromagnets such as Lu 2 V 2 O 7 , and will extend the basis for magnonics applications in the future.