Zig-Zag ground state and potential Kitaev interactions in the spin-1 honeycomb material KNiAsO₄

Despite the exciting implications of the Kitaev spin Hamiltonian, finding and confirming the quantum spin-liquid state have proven incredibly difficult. Recently, the applicability of the model has been expanded through the development of a microscopic description of a spin-1 Kitaev interaction. Here we explore a candidate spin-1 honeycomb system, KNiAsO₄, which meets many of the proposed criteria to generate such an interaction. Neutron diffraction measurements show magnetic order at 19 K which results in the well-known “zig-zag” magnetic structure thought to be adjacent to the spin-liquid ground state. Inelastic neutron scattering experiments show a well-defined gapped spin-wave spectrum with no evidence of the fractionalized excitations found in the spin-1/2 model. Modeling of the spin waves using linear spin-wave theory together with a machine learning based optimization shows that the extended Kitaev spin Hamiltonian is generally necessary to model the spectra and reproduce the observed magnetic order. These results suggest that KNiAsO₄ may be a candidate to study spin-1 Kitaev physics.