Direct observation of the soft-mode dispersion in the incipient ferroelectric KTaO3 -: art. no. 092106

Far-infrared dispersion of the complex dielectric constant in incipient ferroelectric KTaO3 has been revealed by terahertz time-domain spectroscopy (THz-TDS) in the temperature range from 8 K to 300 K. The real part of the complex dielectric constant in the far-infrared region is larger than the static permittivity. Through the analysis using a single Lorentz oscillator model, we conclude that the origin of the extremely large static permittivity in KTaO3 and its anomalous behavior at low temperatures are almost fully attributed to the TO1 mode dispersion and the suppression of the softening.