Strain-induced metal-insulator transition in t 2 g electron system of perovskite titanate S m 0.5 C a 0.5 Ti O 3 films

We have demonstrated a strain-induced metal-insulator transition for weak Jahn-Teller effects in a ${t}_{2g}$ electron system of $\mathrm{S}{\mathrm{m}}_{0.5}\mathrm{C}{\mathrm{a}}_{0.5}\mathrm{Ti}{\mathrm{O}}_{3}$, which has metallic ground states in the bulk. A clear variation of electronic properties in $\mathrm{S}{\mathrm{m}}_{0.5}\mathrm{C}{\mathrm{a}}_{0.5}\mathrm{Ti}{\mathrm{O}}_{3}$ thin films was investigated as a function of epitaxial stain by changing a substrate and the film thickness. Under strong biaxial tensile strain, metallic behaviors were completely eliminated, as evidenced by the temperature dependence of resistivity. The observed metal-insulator transition was consistent with the behavior of the Ti $3d$ density of states at the Fermi level seen in valence band hard x-ray photoemission spectra.