DFT+DMFT Study of Strain Effect on a Kitaev Material, Na₃Co₂SbO₆

Na₃Co₂SbO₆ in a honeycomb structure has been argued as a promising material candidate for realizing the quantum spin liquid (QSL) phase due to a large Kitaev spin exchange interaction as suggested by Liu et al. [Phys. Rev. Lett. 125, 047201 (2020)]. At low temperature, the Co²⁺ ion (d⁷ ) exhibits a high-spin ground state, and tuning the trigonal crystal field between a_1g and e^'_g orbitals is crucial to realize the QSL phase. Here, we show how the strain effect can change both the trigonal crystal field and the Jahn-Teller (JT) distortion splitting in Na₃Co₂SbO₆, and how the correlated electronic structure varies due to the structural change using density function theory plus dynamical mean field theory (DFT+DMFT). We will show that the JT splitting can further split e^'_g orbitals, and the splitting can be tunable under the strain effect although their electronic structures are still similar. Under tensile strain, the a_1g orbital level becomes higher than the e^'_g one, and its hole occupancy gets close to one, resulting in the Mott insulating state. Finally, we will discuss the effect of electronic structure changes on the spin exchange interactions of the spin-orbit entangled pseudospin J_eff=1/2 state.