Investigation of spin excitations in a spin-1 Kitaev candidate material

The Kitaev model is an exactly solvable quantum-spin-liquid model defined on a honeycomb lattice with S = 1/2. The key element underlying this model is the bond-anisotropic Kitaev interaction. More recently, we extend the Kitaev physics to a higher-spin system, where we find in a honeycomb-lattice antiferromagnet Na3Ni2BiO6 that there is a profound 1/3 magnetization plateau, which is stabilized by the Kitaev interaction. However, its sister compound Na3Ni2SbO6 (NNSO) exhibits a different behavior. Our theoretical calculations suggest a potential weakening of the Kitaev interaction in NNSO, possibly leading to the prominence of biquadratic exchange. Hence, NNSO not only serves as an ideal platform for studying the impact of SOC on Kitaev interactions but also presents a unique opportunity to explore the uncommon biquadratic exchange interaction.