Structural and electronic properties of epitaxially-strained LaVO₃ from density functional theory and dynamical mean-field theory

The effect of epitaxial strain on the structural and electronic properties of LaVO_3 is investigated through density functional theory (DFT) and dynamical mean field theory (DMFT). Two different growth orientations of the crystal are considered, one preserving the bulk Pbnm space-group symmetry and another giving rise to a symmetry lowering to P2_1/m. In the nonmagnetic DFT structures, the two growth orientations are equally favored for all tensile strains considered here, as well as for compressive strains weaker than -3%. For stronger compressive strains, the P2_1/m orientation is favored and shows a complete suppression of octahedral tilts along the out-of-plane direction. Magnetically-ordered structures do not show a complete tilt suppression, but the trend points to a similar reduction of the out-of-plane V-O-V bond angles under compressive strain. Our DMFT calculations show that, in accord with room-temperature experiments, the bulk paramagnetic Mott-insulating state of LaVO_3 is robust against epitaxial strains attainable in thin films, since the suppression of orbital fluctuations counteracts the effect of bandwidth increase with compressive strain. Under stronger compressive strains, the straightening of the V-O-V bonds in the P2_1/m geometry interferes with the suppression of orbital fluctuations and hence perturbs the Mott phase more strongly, albeit not enough to achieve a metallic phase.