Nanoscale Disorder inCaCu3Ti4O12: A New Route to the Enhanced Dielectric Response

Abstract

Significant nanoscale disorder of Cu and Ca atomic substitution is observed in ${\mathrm{CaCu}}_{3}{\mathrm{Ti}}_{4}{\mathrm{O}}_{12}$, based on our integrated study using quantitative electron diffraction and extended x-ray absorption fine structure. Unambiguous identification of this previously omitted disorder is made possible by the unique sensitivity of these probes to valence-electron distribution and short-range order. Furthermore, first-principles-based theoretical analysis indicates that the Ca-site Cu atoms possess partially filled degenerate ${e}_{g}$ states, suggesting significant boost of dielectric response from additional low-energy electronic contributions. Our study points to a new route of enhancing dielectric response in transitional metal oxides by exploiting the strong electronic correlation beyond classical static pictures.