Intrinsic topological magnons in arrays of magnetic dipoles

TL;DR

This paper investigates how periodic modulation of magnetic dipoles creates topological magnon states with tunable spectral gaps, edge modes, and thermal transport properties, revealing rich topological phenomena in magnetic systems.

Contribution

It introduces a simple magnetic dipole array model that exhibits topological magnon phases, including fractional Zak numbers and edge states, controlled by modulation amplitude.

Findings

Frequency gaps and magnon speeds are tunable via modulation.

Fractional Zak number phase and edge states appear in 1D systems.

Band touching causes Chern number exchange and sign reversal of thermal conductivity.

Abstract

We study a simple magnetic system composed of periodically modulated magnetic dipoles with an easy axis. Upon adjusting the modulation amplitude alone, chains and two-dimensional stacked chains exhibit a rich magnon spectrum where frequency gaps and magnon speeds are easily manipulable. The blend of anisotropy due to dipolar interactions between magnets and geometrical modulation induces a magnetic phase with fractional Zak number in infinite chains and end states in open one-dimensional systems. In two dimensions it gives rise to topological modes at the edges of stripes. Tuning the amplitude in two-dimensional lattices causes a band touching, which triggers the exchange of the Chern numbers of the volume bands and switches the sign of the thermal conductivity.