Strain-induced topological transition inSrRu2O6andCaOs2O6

The topological property of ${\mathrm{SrRu}}₂{\mathrm{O}}₆$ and isostructural ${\mathrm{CaOs}}₂{\mathrm{O}}₆$ under various strain conditions is investigated using density functional theory. Based on an analysis of parity eigenvalues, we anticipate that a three-dimensional strong topological insulating state should be realized when band inversion is induced at the A point in the hexagonal Brillouin zone. For ${\mathrm{SrRu}}₂{\mathrm{O}}₆$, such a transition requires rather unrealistic tuning, where only the $c$ axis is reduced while other structural parameters are unchanged. However, given the larger spin-orbit coupling and smaller lattice constants in ${\mathrm{CaOs}}₂{\mathrm{O}}₆$, the desired topological transition does occur under uniform compressive strain. Our study paves a way to realize a topological insulating state in a complex oxide, which has not been experimentally demonstrated so far.