LAUSR

Iridate oxides on a honeycomb lattice are considered promising candidates for realization of quantum spin liquid states. We investigate the magnetic couplings in a structural model for a honeycomb iridate ${\mathrm{K}}_{2}{\mathrm{IrO}}_{3}$, with ${C}_{3}$ point-group symmetry at the Ir sites, which is an end member of the recently synthesized iridate family ${\mathrm{K}}_{x}{\mathrm{Ir}}_{y}{\mathrm{O}}_{2}$. Using ab initio quantum chemical methods, we elucidate the subtle relationship between the real space symmetry and magnetic anisotropy and show that the higher point-group symmetry leads to high frustration with strong magnetic anisotropy driven by the unusually large off-diagonal exchange couplings ($\mathrm{\ensuremath{\Gamma}}$'s) as opposed to other spin-liquid candidates considered so far. Consequently, large quantum fluctuations imply lack of magnetic ordering consistent with the experiments. Exact diagonalization calculations for the fully anisotropic $K\ensuremath{-}J\ensuremath{-}\mathrm{\ensuremath{\Gamma}}$ Hamiltonian reveal the importance of the off-diagonal anisotropic exchange couplings in stabilizing a spin liquid state and highlight an alternative route to stabilize spin liquid states for ferromagnetic $K$.