X-ray Absorption Studies of Structural Distortion in Ag₃LiIr₂O₆

Strong spin orbit coupling in honeycomb iridates can give rise to J_eff=1/2 states with Kitaev interactions. This is realized in alpha-Li₂IrO₃ and Na₂IrO₃, but magnetic ordering occurs at low temperatures likely due to Heisenberg interactions. Ag₃LiIr₂O₆ is a recently synthesized Kitaev spin liquid candidate similar to α-Li₂IrO₃, but with the interplanar Li replaced by Ag. Thermodynamic measurements confirmed the absence of long range order. However, the higher covalency of the Ag atoms may distort the IrO₆ octahedra. Large enough distortion would mix the J_eff=1/2 and J_eff=3/2 states, invalidating the J_eff=1/2 picture. To investigate the local structure and electronic states, we carried out x-ray absorption spectroscopy measurements at the Ir L₂ and L₃ edges in Ag₃LiIr₂O₆ and other iridates. The near edge structure (XANES) suggests spin orbit coupling with strength comparable to that in α-Li₂IrO₃ and shows signs of mixed valency. From the extended x-ray absorption fine structure (EXAFS), we extract temperature dependent Ir-O bond lengths to track distortion. These results will help determine the proximity of Ag₃LiIr₂O₆ to the Kitaev model.