  Direct experimental estimations of the low-energy ($1.5\sim10$ meV) complex
dielectric constants spectrum and its temperature variation have been
investigated for La$_{0.7}$Ca$_{0.3}$MnO$_3$ thin films using terahertz
time-domain spectroscopy. At low temperatures, a clear Drude-term emerges. With
increasing temperature, the scattering rate increases, while the plasma
frequency decreases, derived both from a simple Drude model. Finally, a
Drude-term submerges well below the insulator-metal transition temperature. On
the basis of the present results, low-energy charge dynamics are discussed.
