# Dirac magnons in a honeycomb lattice quantum XY magnet CoTiO3

## TL;DR

This study reveals Dirac magnons in the 3D honeycomb lattice magnet CoTiO3, demonstrating its potential as a model system for exploring Dirac bosons in quantum XY magnets.

## Contribution

First observation of Dirac magnons in a 3D honeycomb lattice quantum XY magnet CoTiO3, highlighting strong easy-plane anisotropy and a gapless Dirac cone.

## Key findings

- Dirac magnon dispersion with a gapless Dirac cone
- Strong easy-plane exchange anisotropy observed
- CoTiO3 identified as a model for Dirac bosons in 3D

## Abstract

The discovery of massless Dirac electrons in graphene and topological Dirac-Weyl materials has prompted a broad search for bosonic analogues of such Dirac particles. Recent experiments have found evidence for Dirac magnons above an Ising-like ferromagnetic ground state in a two-dimensional (2D) kagome lattice magnet and in the van der Waals layered honeycomb crystal CrI$_3$, and in a 3D Heisenberg magnet Cu$_3$TeO$_6$. Here we report on our inelastic neutron scattering investigation on large single crystals of a stacked honeycomb lattice magnet CoTiO$_3$, which is part of a broad family of ilmenite materials. The magnetically ordered ground state of CoTiO$_3$ features ferromagnetic layers of Co$^{2+}$, stacked antiferromagnetically along the $c$-axis. We discover that the magnon dispersion relation exhibits strong easy-plane exchange anisotropy and hosts a clear gapless Dirac cone along the edge of the 3D Brillouin zone. Our results establish CoTiO$_3$ as a model pseudospin-$1/2$ material to study interacting Dirac bosons in a 3D quantum XY magnet.