First demonstration of tuning between the Kitaev and Ising limits in a honeycomb lattice

Abstract

Recent observations of novel spin-orbit coupled states have generated tremendous interest in $4d/5d$ transition metal systems. A prime example is the $J_{\text{eff}}=\frac{1}{2}$ state in iridate materials and $\alpha$-RuCl${}_3$ that drives Kitaev interactions. Here, by tuning the competition between spin-orbit interaction (${\lambda }_{\text{SOC}}$) and trigonal crystal field splitting (${\Delta }_{\text{T}}$), we restructure the spin-orbital wave functions into a novel $\mu =\frac{1}{2}$ state that drives Ising interactions. This is done via a topochemical reaction that converts Li${}_2$RhO${}_3$ to Ag${}_3$LiRh${}_2$O${}_6$, leading to an enhanced trigonal distortion and a diminished spin-orbit coupling in the latter compound. Using perturbation theory, we present an explicit expression for the new $\mu =\frac{1}{2}$ state in the limit ${\Delta }_{\text{T}}\gg {\lambda }_{\text{SOC}}$ realized in Ag${}_3$LiRh${}_2$O${}_6$, different from the conventional $J_{\text{eff}}=\frac{1}{2}$ state in the limit ${\lambda }_{\text{SOC}}\gg {\Delta }_{\text{T}}$ realized in Li${}_2$RhO${}_3$. The change of ground state is followed by a dramatic change of magnetism from a 6 K spin-glass in Li${}_2$RhO${}_3$ to a 94 K antiferromagnet in Ag${}_3$LiRh${}_2$O${}_6$. These results open a pathway for tuning materials between the two limits and creating a rich magnetic phase diagram.

22 pages, 4 figures

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Cited by in corpus (1)

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