Unusual spin dynamics in the low-temperature magnetically ordered state of Ag3LiIr2O6

Recently, there have been contrary claims of Kitaev spin-liquid behavior and ordered behavior in the honeycomb compound ${\mathrm{Ag}}_{3}\mathrm{Li}{\mathrm{Ir}}_{2}{\mathrm{O}}_{6}$ based on various experimental signatures. Our investigations on this system reveal a low-temperature ordered state with persistent dynamics down to the lowest temperatures. Magnetic order is confirmed by clear oscillations in the muon spin relaxation ($\ensuremath{\mu}\mathrm{SR}$) time spectrum below 9 K until 52 mK. Coincidentally in $^{7}\mathrm{Li}$ nuclear magnetic resonance, a wipeout of the signal is observed below $\ensuremath{\sim}10$ K, which again strongly indicates magnetic order in the low-temperature regime. This is supported by our density functional theory calculations which show an appreciable Heisenberg exchange term in the spin Hamiltonian that favors magnetic ordering. The $^{7}\mathrm{Li}$ shift and spin-lattice relaxation rate also show anomalies at $\ensuremath{\sim}50$ K. They are likely related to the onset of dynamic magnetic correlations, but their origin is not completely clear. Detailed analysis of our $\ensuremath{\mu}\mathrm{SR}$ data is consistent with a coexistence of incommensurate N\'eel and striped environments. A significant and undiminished dynamical relaxation rate ($\ensuremath{\sim}5$ MHz) as seen in $\ensuremath{\mu}\mathrm{SR}$ deep into the ordered phase indicates enhanced quantum fluctuations in the ordered state.