Doping Dependence of the Electronic Structure of Ba_{1-x}K_{x}BiO_{3} Studied by X-Ray Absorption Spectroscopy

TL;DR

This study investigates how the electronic structure of Ba_{1-x}K_{x}BiO_{3} changes with doping using X-ray absorption and photoemission spectroscopy, revealing a metal-insulator transition and deviations from simple band models.

Contribution

It provides detailed doping-dependent spectroscopic data and compares experimental results with band-structure calculations, highlighting differences from similar compounds.

Findings

Spectral weight increases with hole doping, indicating a metal-insulator transition.

Chemical potential shifts are observed and are slower than rigid band model predictions.

Distinct doping dependence compared to BaPb_{1-x}Bi_{x}O_{3} was found.

Abstract

We have performed x-ray absorption spectroscopy (XAS) and x-ray photoemission spectroscopy (XPS) studies of single crystal Ba_{1-x}K_{x}BiO_{3} (BKBO) covering the whole composition range $0 \leq x \leq 0.60$. Several features in the oxygen 1\textit{s} core XAS spectra show systematic changes with $x$. Spectral weight around the absorption threshold increases with hole doping and shows a finite jump between $x=0.30$ and 0.40, which signals the metal-insulator transition. We have compared the obtained results with band-structure calculations. Comparison with the XAS results of BaPb_{1-x}Bi_{x}O_{3} has revealed quite different doping dependences between BKBO and BPBO. We have also observed systematic core-level shifts in the XPS spectra as well as in the XAS threshold as functions of $x$, which can be attributed to a chemical potential shift accompanying the hole doping. The observed chemical potential shift is found to be slower than that predicted by the rigid band model based on the band-structure calculations.