Metal Insulator Transitions, Strain and Electron-Lattice Coupling in Calcium Ruthenates*

A general Ginzburg-Landau free energy is proposed for the metal-insulator transition (MIT) in correlated oxides, which incorporates magnetism, octahedral distortions, strain as well as the electronic transition. The theory is used to elucidate important experimental features observed across thermal-induced and current induced MIT in 2-1-4 and Ti-doped 3-2-7 calcium ruthenate compounds, including the coexistence of metallic and insulating domains, occurrence, orientation and lengths of stripes at the domain boundaries, as well as the impact of uniaxial and biaxial strain on the transition temperatures and elasto-resistance. Generalzation to MIT in other systems is presented.