Spectral functions in doped transition metal oxides

TL;DR

This paper combines experimental photoemission data with a new theoretical approach to better understand the spectral properties of electron-doped SrTiO₃, revealing limitations of traditional models and emphasizing the importance of inhomogeneity.

Contribution

It introduces a novel theoretical method accounting for inhomogeneity in doped transition metal oxides, improving agreement with experimental spectra over standard homogeneous models.

Findings

Spectral features are influenced by electron correlation effects.

Standard Hubbard models do not fully explain spectral evolution.

Inhomogeneous models align better with experimental data.

Abstract

We present experimental photoemission and inverse photoemission spectra of SrTiO$_{3- \delta}$ representing electron doped $d^0$ systems. Photoemission spectra in presence of electron doping exhibit prominent features arising from electron correlation effects, while the inverse photoemssion spectra are dominated by spectral features explainable within single-particle approaches. We show that such a spectral evolution in chemically doped correlated systems is not compatible with expectations based on Hubbard or any other similar model. We present a new theoretical approach taking into account the inhomogeneity of the `real' system which gives qualitatively different results compared to standard `homogeneous' models and is in quantitative agreement with experiments.