Large spectral weight transfer in optical conductivity of SrTiO$_{3}$ induced by intrinsic vacancies

TL;DR

This study reveals significant spectral weight transfer in SrTiO$_{3}$'s optical conductivity caused by intrinsic vacancies, highlighting the role of strong correlations and orbital reconstruction in its electronic structure.

Contribution

It provides a systematic analysis of how cation and anion vacancies affect optical conductivity and spectral weight transfer in SrTiO$_{3}$, introducing new insights into vacancy-induced electronic changes.

Findings

Large spectral weight transfer from 35 eV to 0.5 eV in Ti vacancies

Mid-gap states indicating strong correlations

Changes in optical conductivity from 7.4 eV to 35 eV in O vacancies

Abstract

The optical conductivity ($\sigma_{1}$) of SrTiO$_{3}$ for various vacancies has been systematically studied using a combination of ultraviolet - vacuum ultraviolet (UV-VUV) reflectivity and spectroscopic ellipsometry. For cation (Ti) vacancies, $\sigma_{1}$ shows large spectral weight transfer over a wide range of energy from as high as 35 eV to as low as 0.5 eV and the presence of mid-gap states, suggesting that strong correlations play an important role. While for anion (O) vacancies $\sigma_{1}$ shows changes from 7.4 eV up to 35 eV. These unexpected results can be explained in terms of orbital reconstruction.