Signatures of Kitaev interactions in the van der Waals ferromagnet VI3

TL;DR

This study uses neutron scattering to reveal Kitaev interactions in VI3, a van der Waals ferromagnet, providing evidence for bond-dependent magnetic interactions that could host exotic quantum states.

Contribution

It demonstrates the presence of significant Kitaev interactions in VI3 through detailed experimental and theoretical analysis, advancing the search for Kitaev materials.

Findings

Highly anisotropic magnetic excitations observed

Kitaev interaction model accurately describes excitations

Supports potential for quantum spin liquid states in VI3

Abstract

Materials manifesting the Kitaev model, characterized by bond-dependent interactions on a honeycomb lattice, can host exotic phenomena like quantum spin liquid states and topological magnetic excitations. However, finding such materials remains a formidable challenge. Here, we report high-resolution inelastic neutron scattering measurements performed on VI3, a van der Waals ferromagnetic Mott insulator, covering a wide range of reciprocal space. Our measurements unveil highly anisotropic magnetic excitations in momentum space. Through a comprehensive comparative analysis of various models that incorporate diverse symmetry-allowed magnetic interactions, we find the observed excitations are well captured by a model with a large bond-dependent Kitaev interaction. These results not only help to understand the intriguing properties of VI3, such as the pronounced anomalous thermal Hall effects and strong pressure/structure dependence of magnetism, but also open a new avenue for exploring Kitaev physics.