Strain control of orbital polarization and correlated metal-insulator transition in La₂CoMnO₆ from first principles

Transition metal oxides show rich physical properties which are often influenced by external perturbation. Here, we report by first-principles calculations that strain enables switching of orbital occupancy of Co ² in La₂CoMnO₆ and hence modifies electronic structure of La₂CoMnO₆. We find a metal-insulator transition in La₂CoMnO₆, which originates from the interplay between the strain induced lattice distortion and electron correlations. Such transition is understood upon the orbital polarization of Co², which takes on the d xz / yz character under compression, yet switches to the d x 2 - y 2 character under tension. The orbital switching presented should hold promise for many technological applications.