Kitaev interactions in the van der Waals antiferromagnet VBr3

TL;DR

This study investigates the magnetic excitations in VBr3, a van der Waals antiferromagnet with a honeycomb lattice, revealing significant Kitaev interactions and proposing ligand engineering to tune quantum properties.

Contribution

It identifies VBr3 as a new Kitaev magnet and demonstrates how ligand engineering can modulate Kitaev interactions in van der Waals materials.

Findings

Observation of low-energy spin excitations with a 2.5 meV spin gap.

Effective spin Hamiltonian includes Kitaev, biquadratic, and Heisenberg interactions.

VBr3 is established as a new candidate for Kitaev quantum materials.

Abstract

Van der Waals materials hosting Kitaev interactions are promising platforms for exploring exotic quantum phenomena. Here, we report inelastic neutron scattering investigations of the van der Waals antiferromagnet VBr3, which forms a honeycomb lattice structure at room temperature and exhibits zigzag-type magnetic order below 26.5 K. Our observations reveal distinctive low-energy spin excitations arising from gamma, gamma', and M' points, each featuring a spin gap of around 2.5 meV. The overall spin excitation spectra can be effectively described by a spin Hamiltonian incorporating substantial nearest-neighbor Kitaev and biquadratic interactions, along with Heisenberg interactions. Our findings not only establish VBr3 as a new Kitaev magnet but also suggest that ligand engineering may provide a promising strategy to modulate Kitaev interactions, offering new opportunities for designing Kitaev materials with tailored quantum properties.