Low-energy charge dynamics in La${}_{\text{0.7}}$Ca${}_{\text{0.3}}$MnO${}_{\text{3}}$: THz time-domain spectroscopic studies

Direct experimental estimations of the low-energy ($1.5\sim 10$ 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.