Kitaev materials

In transition-metal compounds with partially filled 4d and 5d shells spin–orbit entanglement, electronic correlations, and crystal-field effects conspire to give rise to a variety of novel forms of topological quantum matter. This includes Kitaev materials — a family of spin–orbit assisted Mott insulators, in which local, spin–orbit entangled j=1/2 moments form that are subject to dominant bond-directional Ising exchange interactions. On a conceptual level, Kitaev materials attract much interest for their potential for unconventional forms of magnetism, such as spin liquid physics in two- and three-dimensional lattice geometries or the formation of non-trivial spin textures. Experimentally, a number of Kitaev materials have been synthesized, which includes the honeycomb materials Na2IrO3, α-Li2IrO3, H3LiIr2O6, and, most prominently, α-RuCl3, the triangular materials Ba3IrxTi3−xO9, as well as the three-dimensional hyper-honeycomb and stripy-honeycomb materials β-Li2IrO3 and γ-Li2IrO3. We provide a short review of the current status of the theoretical and experimental exploration of these Kitaev materials.