Large spectral weight transfer in optical conductivity of SrTiO$_{3}$   induced by intrinsic vacancies
  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. 
Teguh C. Asmara, Xiao Wang, Iman Santoso, Qinfang Zhang, Tomonori   Shirakawa, Dongchen Qi, Aleksei Kotlov, Mallikarjuna R. ...
cond-mat.str-el cond-mat.mtrl-sci