Coherent and Incoherent States of Electron-doped SrTiO3

TL;DR

This study investigates the electronic states in Nb-doped SrTiO3, revealing distinct coherent and incoherent states with specific orbital characters, and discusses their spectral evolution and underlying mechanisms.

Contribution

It provides new insights into the nature and origin of coherent and incoherent states in electron-doped SrTiO3 using resonant photoemission spectroscopy.

Findings

Coherent state at EF is mainly Ti 3d character.

Incoherent in-gap state is a mix of Ti 3d and O 2p states.

Spectral-weight transfer from CS to IGS explained by d-p hybridization.

Abstract

Resonant photoemission at the Ti 2p and O 1s edges on a Nb-doped SrTiO3 thin film revealed that the coherent state (CS) at the Fermi level (EF) had mainly Ti 3d character whereas the incoherent in-gap state (IGS) positioned ~1.5 eV below EF had mixed character of Ti 3d and O 2p states. This indicates that the IGS is formed by a spectral-weight transfer from the CS and subsequent spectral-weight redistribution through d-p hybridization. We discuss the evolution of the excitation spectrum with 3d band filling and rationalize the IGS through a mechanism similar to that proposed by Haldane and Anderson.