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 interest in 4d/5d transition metal systems. A prime example is the state in iridate materials and α-RuCl3 that drives Kitaev interactions. Here, by tuning the competition between spin-orbit interaction (λSOC) and trigonal crystal field (ΔT), we restructure the spin-orbital wave functions into a previously unobserved state that drives Ising interactions. This is done via a topochemical reaction that converts Li2RhO3 to Ag3LiRh2O6. Using perturbation theory, we present an explicit expression for the state in the limit ΔT ≫ λSOC realized in Ag3LiRh2O6, different from the conventional state in the limit λSOC ≫ ΔT realized in Li2RhO3. The change of ground state is followed by a marked change of magnetism from a 6 K spin-glass in Li2RhO3 to a 94 K antiferromagnet in Ag3LiRh2O6.