Electron-spectroscopic investigation of the metal-insulator transition in Sr₂Ru_1−xTi_xO₄ (x=0-0.6)

Abstract

We investigate the nature and origin of the metal-insulator transition in Sr₂Ru_1−xTi_xO₄ 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 ≥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.