thin films deviate from Fermi liquid predictions?

Orthorhombic pervoskites SrRuO₃ and CaRuO₃ are strongly correlated metals with unusual transport properties. Previous optics studies in the infrared and terahertz range shows non-Drude dynamics and fractional scattering rates at low temperatures which seems to contradict a Fermi-liquid picture with long-lived quasiparticles. Here we present time domain THz measurements of clean thin films of SrRuO₃ and CaRuO₃. Our results demonstrate for both materials the low temperature conductivity shows a narrow Drude-like peak and can be fitted with two Drude terms. The conductivity crosses over to become less coherent at higher temperatures. Comparison with Fermi liquid scaling theories shows that CaRuO₃ is more anomalous than SrRuO₃ probably owing to spin fluctuations in the paramagnetic phase.