Spin-orbit coupled insulators and metals on the verge of Kitaev spin liquids in ilmenite heterostructures*

Competition and cooperation between the relativistic spin-orbit coupling and electron correlations give rise to various exotic quantum phenomena in solids. One such example is quantum spin liquids in magnets, which exhibit remarkable features such as topological orders and fractional excitations and could be realized in the Kitaev honeycomb model. Here we theoretically investigate hexagonal heterostructures including a candidate for the Kitaev magnets, an ilmenite oxide MgIrO₃, to actively manipulate the electronic and magnetic properties toward the realization of the Kitaev spin liquids, by combining first-principles calculations and the effective model approaches. For three different types of bilayers MgIrO₃/ATiO₃ with A=Mn, Fe, Co, and Ni, we find that the spin-orbit coupled bands characterized by the pseudospin j_eff = 1/2, crucially important for the Kitaev-type interactions, are retained in the MgIrO₃ layer for all the heterostructures, but the band gap and the magnetic state depend on the types of the heterostructures as well as the A atoms. In particular, one type becomes metallic irrespective of A, while the other two are insulating. We show that the insulating cases realize dominant Kitaev-type interactions with different combinations of subdominant interactions depending on the type and A. Our results indicate that these hexagonal heterostructures are a good platform for engineering the magnetism and insulator-metal transitions in the spin-orbit coupled correlated materials.