Molecular Orbitals from Chemical Pressure in Ag₃LiIr₂O₆

The honeycomb iridates, α-Li2IrO3 and Na2PrO3 are among the closest material realizations of the Kitaev model. Although dominant Heisenberg exchange interactions in both of these compounds result in low temperature magnetic order, Kitaev interactions are known to be strong. The relevance of the Kitaev model stems from a balance of electronic correlations and spin orbit coupling that result in a localized spin-orbit entangled j_eff=1/2 magnetic degree of freedom. Recently, a new honeycomb iridate, Ag₃LiIr₂O₆ was shown to exhibit thermodynamic signatures of close proximity to the spin liquid limit [1]. In this talk, I will discuss a series of x-ray spectroscopy measurements on Ag₃LiIr₂O₆ that reveal a strong modification of the Ir electronic structure from the parent α-Li2IrO6 such that a delocalized, molecular orbital picture is more appropriate for Ag₃LiIr₂O₆. These measurements show how chemical pressure can influence the single ion state in transition metal magnets and provide further evidence for the fragility of the local j_eff=1/2 picture. I will discuss these results in the context of the Kitaev model and possible magnetic ground states in Ag₃LiIr₂O₆.

[1] Faranak Bahrami, William Lafargue-Dit-Hauret, Oleg I. Lebedev, Roman Movshovich, Hung-Yu Yang, David Broido, Xavier Rocquefelte, and Fazel Tafti. “Thermodynamic Evidence of Proximity to a Kitaev Spin Liquid in Ag₃LiIr₂O₆”. Phys. Rev. Lett. 123, 237203 (2019)