Large off-diagonal exchange coupling driven magnetic anisotropy and spin liquid states in the C₃-symmetric iridate K₂IrO₃

Honeycomb lattice spin-orbit insulators are promising candidates for realization of quantum spin liquid states. The iridate oxide K₂IrO₃ is an end member of the recently synthesized iridate family K_xIr_yO₂, and features a C₃ point-group symmetry at the Ir sites. Using ab-initio techniques, we investigate the magnetic couplings in the proposed structural model for K₂IrO₃. We find that the higher point-group symmetry leads to strong magnetic anisotropy driven by the unusually large off-diagonal exchange couplings (Γ's) as opposed to other spin liquid candidates considered so far. High magnetic frustration and large quantum fluctuations imply lack of magnetic ordering consistent with the experiments. Exact diagonalization calculations for the fully anisotropic K−J−Γ Hamiltonian reveal a rich phase diagram with competing magnetic as well as spin liquid states. Our study points out the importance of the Γ's in stabilizing a spin liquid state and highlights an alternative route to stabilize spin liquid states for ferromagnetic K.

References:
[1] R. Yadav, et al. Phys. Rev. B 100, 144422 (2019).