Kitaev Materials

TL;DR

Kitaev materials are a class of spin-orbit entangled Mott insulators with bond-directional interactions, exhibiting unconventional magnetism and potential quantum spin liquid states, with several compounds experimentally realized.

Contribution

This review summarizes recent theoretical and experimental progress in understanding and synthesizing various Kitaev materials across different lattice geometries.

Findings

Multiple Kitaev materials have been synthesized, including honeycomb, triangular, and three-dimensional structures.

These materials exhibit diverse magnetic behaviors, including potential spin liquid phases.

Experimental studies have advanced understanding of their magnetic and electronic properties.

Abstract

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 strong bond-directional interactions. On a conceptual level, Kitaev materials attract much interest for their 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 Na$_2$IrO$_3$, $\alpha$-Li$_2$IrO$_3$, and RuCl$_3$, the triangular materials Ba$_3$Ir$_x$Ti$_{3-x}$O$_9$, as well as the three-dimensional hyper-honeycomb and stripy-honeycomb materials $\beta$-Li$_2$IrO$_3$ and $\gamma$-Li$_2$IrO$_3$. These lecture notes provide a short review of the current status of the theoretical and experimental exploration of these Kitaev materials.