Electron-correlation effects on the properties of ${\mathrm{La}}_{\mathit{x}}$${\mathrm{Sr}}_{1\mathrm{-}\mathit{x}}$${\mathrm{TiO}}_3$

A theoretical study of the electron-correlation effects on the properties of ${\mathrm{La}}_{\mathit{x}}$${\mathrm{Sr}}_{1\mathrm{-}\mathit{x}}$${\mathrm{TiO}}_3$ is presented. Using a single band repulsive Hubbard model employing the Gutzwiller approximation we study the effect of electron correlations on the effective-mass, band narrowing, plasma frequency, and spin susceptibility. The doping dependence of these properties are found to be qualitatively in agreement with recent experimental studies on ${\mathrm{La}}_{\mathit{x}}$${\mathrm{Sr}}_{1\mathrm{-}\mathit{x}}$${\mathrm{TiO}}_3$. We have also proposed a possibility for inducing superconductivity using the idea of proximity effect. The induced superconducting gap in ${\mathrm{La}}_{\mathit{x}}$${\mathrm{Sr}}_{1\mathrm{-}\mathit{x}}$${\mathrm{TiO}}_3$ is predicted to be maximum near the half-filling of the Ti 3d band.