Thermodynamic Evidence of Proximity to a Kitaev Spin-Liquid in Ag$_{3}$LiIr$_{2}$O$_{6}$

Abstract: Kitaev magnets are materials with bond-dependent Ising interactions between localized spins on a honeycomb lattice. Such interactions could lead to a quantum spin-liquid (QSL) ground state at zero temperature. Recent theoretical studies suggest two potential signatures of a QSL at finite temperatures, namely a scaling behavior of thermodynamic quantities in the presence of quenched disorder, and a two-step release of the magnetic entropy. Here, we present both signatures in Ag${3}$LiIr${2}$O${6}$ which is synthesized from $\alpha$-Li${2}$IrO${3}$ by replacing the inter-layer Li atoms with Ag atoms. In addition, the DC susceptibility data confirm absence of a long-range order, and the AC susceptibility data rule out a spin-glass transition. These observations suggest a closer proximity to the QSL in Ag${3}$LiIr${2}$O${6}$ compared to its parent compound $\alpha$-Li${2}$IrO${3}$ that orders at 15 K. We discuss an enhanced spin-orbit coupling due to a mixing between silver d and oxygen p orbitals as a potential underlying mechanism.