Electron-spectroscopic investigation of the metal-insulator transition inSr2Ru1−xTixO4(x=0–0.6)

Abstract

We investigate the nature and origin of the metal-insulator transition in ${\mathrm{Sr}}_{2}{\mathrm{Ru}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}{\mathrm{O}}_{4}$ as a function of increasing Ti content $(x)$. Employing detailed core, valence, and conduction band studies with x-ray and ultraviolet photoelectron spectroscopies along with Bremsstrahlung isochromat spectroscopy, it is shown that a hard gap opens up for Ti content $\ensuremath{\geqslant}0.2$, while compositions with $x<0.2$ exhibit finite intensity at the Fermi energy, ${E}_{F}$. This establishes that the metal-insulator transition in this homovalent substituted series of compounds is driven by Coulomb interaction leading to the formation of a Mott gap, in contrast to transitions driven by disorder effects or band filling.