Dirac Magnon in Honeycomb Lattice Magnet NiTiO3

TL;DR

This study reports the observation of Dirac magnons in NiTiO3, a honeycomb lattice magnet, through inelastic neutron scattering and theoretical modeling, revealing Dirac nodal lines and complex spin wave excitations.

Contribution

First experimental detection of Dirac magnons in NiTiO3, supported by linear spin wave theory and calculations of Dirac nodal lines in a honeycomb lattice magnet.

Findings

Observation of 3.7 meV spin wave excitations

Detection of crossing structures at the K point indicating Dirac magnons

Theoretical prediction of Dirac nodal lines in NiTiO3

Abstract

We performed inelastic neutron scattering experiments on single-crystal samples of the honeycomb lattice magnet, ilmenite NiTiO3. Below the Neel temperature of 22 K, spin wave excitations with a band energy of 3.7 meV were observed. The neutron energy spectra were well-reproduced by modeling the system as a ferromagnetic honeycomb lattice with antiferromagnetic interlayer coupling, using linear spin wave theory. Similar to another ilmenite CoTiO3, a crossing structure was observed at the K point, suggesting the resence of Dirac magnons in NiTiO3. Further calculations suggested the formation of Dirac nodal line.