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

Faranak Bahrami; Xiaodong Hu; Yonghua Du; Oleg I. Lebedev; Chennan Wang; Hubertus Luetkens; Gilberto Fabbris; Michael J. Graf; Daniel Haskel; Ying Ran; Fazel Tafti

doi:10.1126/sciadv.abl5671

paper

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

arXiv:2204.07591 · doi:10.1126/sciadv.abl5671

Abstract

Recent observations of novel spin-orbit coupled states have generated tremendous interest in $4 d /5 d$ transition metal systems. A prime example is the $J_{eff} = \frac{1}{2}$ state in iridate materials and $α$ -RuCl $_{3}$ that drives Kitaev interactions. Here, by tuning the competition between spin-orbit interaction ( $λ_{SOC}$ ) and trigonal crystal field splitting ( $Δ_{T}$ ), we restructure the spin-orbital wave functions into a novel $μ = \frac{1}{2}$ 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 $μ = \frac{1}{2}$ state in the limit $Δ_{T} ≫ λ_{SOC}$ realized in Ag $_{3}$ LiRh $_{2}$ O $_{6}$ , different from the conventional $J_{eff} = \frac{1}{2}$ state in the limit $λ_{SOC} ≫ Δ_{T}$ 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.

arXiv comment22 pages, 4 figures

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

Abstract

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