Microscopic modeling of the Kitaev spin liquid candidates Na₃Co₂SbO₆ and Li₃Co₂SbO₆ under uniaxial strain

Abstract:

We study the Kitaev-spin-liquid candidates Na₃Co₂SbO₆ [1] and Li₃Co₂SbO₆ [2] using a microscopic DFT-based analysis. Previous theoretical work suggested [3] that Na₃Co₂SbO₆ is proximate to the spin liquid phase and can be driven there by applying pressure. Following this conjecture, we simulate the effect of uniaxial strain along the c axis. For this purpose, the lattice constant c was changed and the remaining crystal structure was optimized. To get microscopic insights, a Wannier function analysis is performed, which yields local and non-local terms of d and d − p Hamiltonians. From that we determine the crystal field parameters, the spin-orbit coupling constant and the hoppings. A small reduction of the trigonal splitting is found for tensile strain. However, we find that this strain is insufficient to drive the compounds into the spin liquid phase. The theory developed in [1] considers Co²⁺ interactions in a hexagonal edge-sharing geometry. It takes into account the cubic symmetry with trigonal distortions, making it applicable to the real materials. Using the DFT-estimated parameters, we calculate with this theory the exchange parameters Kitaev K, Heisenberg J and the off-diagonal anisotropy terms Γ and Γ′. In this way, we get into the magnetic behavior of this materials under uniaxial strain.

[1] L. Viciu et al., J. Solid State Chem. 180, 1060 (2007).

[2] M. Stratan et al., New J. Chem. 43, 13545 (2019). [3] H. Liu et al., Phys. Rev. Lett. 125, 047201 (2020).

[3] H. Liu et al., Phys. Rev. Lett. 125, 047201 (2020).

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