Kitaev material candidates in the <i>f</i>-block

Na₂MO₃ based Mott insulators have been studied recently as potential candidates to realize Kitaev spin model. 4d⁵ or 5d⁵ systems on a Honeycomb lattice exhibit spin-orbit assisted Mott insulating ground states. At the strong SOC regime, the ground state for these ions in an octahedral crystal field is dominated by J_eff =1/2 states resulting in bond-dependent anisotropic magnetic exchange in the plane, essential to realize the Kitaev spin model. However, candidates to realize the Kitaev spin model are not limited to 4d/5d systems. Lanthanide elements with significant SOC and inherent anisotropy can also be considered in this context. In this talk, I will present our work on a lanthanide based, Kitaev material candidate with a potential J_eff =1/2 ground state. Synthesis and structure of the material will be discussed. Physical property measurements coupled with inelastic neutron scattering results will be utilized to understand the single-ion characteristics of the lanthanide and to unveil the rich low-temperature physics of the material.

Daum, M. J.; Ramanathan, A.; Kolesnikov, A. I.; Calder, S. A.; Mourigal, M.; La Pierre, H. S., Collective excitations in the tetravalent lanthanide honeycomb antiferromagnet, Na₂PrO₃. arXiv preprint arXiv:2010.06741 2020.