Valley Modulation and Single-Edge Transport of Magnons in Staggered Kagome Ferromagnets

TL;DR

This paper explores how valley magnon effects in a kagome ferromagnet can be modulated to achieve single-edge heat transport, revealing new topological phases and edge current behaviors for energy-efficient magnonic devices.

Contribution

It demonstrates valley splitting and topological phase transitions in kagome ferromagnets with staggered exchange and Dzyaloshinskii-Moriya interactions, enabling controlled edge magnon transport.

Findings

Valley magnon Hall effect due to broken inversion symmetry.

Net magnon anomalous Hall effect and topological phase transition.

Localized heat currents at one edge for energy-efficient transport.

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. Moreover, a kagome lattice, as stacking layers of many magnon ferromagnets, also exhibits valley structure in quasiparticle spectra, which are likely to add a new dimension to magnon excitation. Here, we investigate valley magnon and associated valley modulation in a kagome lattice, with staggered exchange interaction and Dzyaloshinskii-Moriya interaction. The staggered exchange interaction breaks spatial inversion symmetry, leading to gapped degenerate valleys at $\pm K$ and consequent valley magnon Hall effect. When the Dzyaloshinskii-Moriya interaction is further included, the valley degeneracy is lifted. As a result, net magnon anomalous Hall effect and topological phase transition are realized. More interestingly, by tuning valley splitting and excitation frequency, heat currents in the kagome strip can be localized at one edge to achieve single-edge transport. Besides, for the kagmon lattice, the edge heat currents include local circulating contribution within triangular fine structure, together with currents flowing parallel to the edges. These findings give full play to spin and valley degrees of freedom and enrich energy-efficient magnonic device paradigms.