Broadband dielectric response of CaCu3Ti4O12: From dc to the electronic transition regime

Abstract

We report on phonon properties and electronic transitions in CaCu3Ti4O12, a material which reveals a colossal dielectric constant at room temperature without any ferroelectric transition. The results of far- and mid-infrared measurements are compared to those obtained by broadband dielectric and millimeter-wave spectroscopy on the same single crystal. The unusual temperature dependence of phonon eigenfrequencies, dampings and ionic plasma frequencies of low lying phonon modes are analyzed and discussed in detail. Electronic excitations below 4 eV are identified as transitions between full and empty hybridized oxygen-copper bands and between oxygen-copper and unoccupied Ti 3d bands. The unusually small band gap determined from the dc-conductivity (~200 meV) compares well with the optical results.

7 pages, 8 figures

References in corpus (6)

• Charge transfer in the high dielectric constant materials CaCu3Ti4O12 and CdCu3Ti4O12
• Broadband dielectric spectroscopy on single-crystalline and ceramic CaCu3Ti4O12
• Dielectric properties and dynamical conductivity of LaTiO3: From dc to optical frequencies
• Polar phonons and spin-phonon coupling in HgCr2S4 and CdCr2S4
• Magnetic-order induced phonon splitting in MnO from far-infrared spectroscopy
• Isosbestic points in the spectral function of correlated electrons

Cited by in corpus (5)

• Colossal dielectric constants in single-crystalline and ceramic CaCu3Ti4O12 investigated by broadband dielectric spectroscopy
• Colossal dielectric constant up to GHz at room temperature
• Anomalous Behavior of the Dielectric and Pyroelectric Responses of Ferroelectric Fine-Grained Ceramics
• Multi-gap absorption in CaCu${}_3$Ti${}_4$O${}_{12}$ and the predictivity of ab initio methods
• Temperature and magnetic field dependent $g$-factors in electron spin resonance spectroscopy