Optical Response of High-Dielectric-Constant Perovskite-Related Oxide
Abstract
Optical conductivity measurements on the perovskite-related oxide CaCu3Ti4O12 provide a hint of the physics underlying the observed giant dielectric effect in this material. A low-frequency vibration displays anomalous behavior, implying that there is a redistribution of charge within the unit cell at low temperature. At infrared frequencies (terahertz), the value for the dielectric constant is ~80 at room temperature, which is far smaller than the value of ~105 obtained at lower radio frequencies (kilohertz). This discrepancy implies the presence of a strong absorption at very low frequencies due to dipole relaxation. At room temperature, the characteristic relaxation times are fast (<~500 nanoseconds) but increase dramatically at low temperature, suggesting that the large change in dielectric constant may be due to a relaxor-like dynamical slowing down of dipolar fluctuations in nanosize domains.
- Publication:
-
Science
- Pub Date:
- July 2001
- DOI:
- 10.1126/science.1061655
- Bibcode:
- 2001Sci...293..673H
- Keywords:
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- PHYSICS