# Weyl and nodal ring magnons in three-dimensional honeycomb lattices

## TL;DR

This paper investigates topological magnon excitations in 3D honeycomb lattices, revealing nodal rings, their gapping into Weyl points via Dzyaloshinskii-Moriya interactions, and associated surface states.

## Contribution

It introduces the existence of nodal ring magnons in 3D honeycomb lattices and demonstrates their transition into Weyl points with surface states, expanding topological magnon research.

## Key findings

- Nodal ring magnon excitations are present on the same plane in momentum space.
- Dzyaloshinskii-Moriya interactions gap the rings into Weyl points with opposite charges.
- Surface states such as drumhead and arc states are observed in the respective phases.

## Abstract

We study the topological properties of magnon excitations in a wide class of three dimensional (3D) honeycomb lattices with ferromagnetic ground states. It is found that they host nodal ring magnon excitations. These rings locate on the same plane in the momentum space. The rings can be gapped by Dzyaloshinskii-Moriya (DM) interactions to form two Weyl points with opposite charges. We explicitly discuss these physics in the simplest 3D honeycomb lattice, the hyperhoneycomb lattice and show drumhead and arc surface states in the nodal ring and Weyl phases, respectively, due to the bulk-boundary correspondence.