Stacking-dependent topological magnons in bilayer CrI$_3$

TL;DR

This paper investigates how stacking configurations and magnetic orderings in bilayer CrI$_3$ influence its magnonic properties, revealing topological bandgaps that are tunable by external magnetic fields, advancing the understanding of topological magnons.

Contribution

It demonstrates that the magnonic behavior and topological bandgap in bilayer CrI$_3$ depend on stacking and magnetic order, introducing tunability via external magnetic fields.

Findings

Topological bandgap opens due to Dzyaloshinskii-Moriya and Kitaev interactions.

Magnonic behavior varies with stacking configuration and magnetic ordering.

External magnetic fields can tune the size and topology of the bandgap.

Abstract

Motivated by the potential of atomically-thin magnets towards tunable high-frequency magnonics, we detail the spin-wave dispersion of bilayer CrI$_3$. We demonstrate that the magnonic behavior of the bilayer strongly depends on its stacking configuration and the interlayer magnetic ordering, where a topological bandgap opens in the dispersion caused by the Dzyaloshinskii-Moriya and Kitaev interactions, classifying bilayer CrI$_3$ as a topological magnon insulator. We further reveal that both size and topology of the bandgap in a CrI$_3$ bilayer with an antiferromagnetic interlayer ordering are tunable by an external magnetic field.