Electron-spectroscopic investigation of metal-insulator transition in Sr2Ru1-xTixO4 (x=0.0-0.6)

TL;DR

This study uses spectroscopic techniques to analyze the metal-insulator transition in Sr2Ru1-xTixO4, revealing a Coulomb interaction-driven Mott gap formation at higher Ti contents.

Contribution

It provides detailed spectroscopic evidence that the transition is due to Coulomb interactions causing a Mott gap, contrasting with disorder or band-filling mechanisms.

Findings

A hard gap appears for x ≥ 0.2

Finite Fermi energy intensity for x < 0.2

Transition driven by Coulomb interaction, not disorder

Abstract

We investigate the nature and origin of the metal-insulator transition in Sr2Ru1-xTixO4 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 greater than equal to 0.2, while compositions with x<0.2 exhibit finite intensity at the Fermi energy. 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 flling.