Charge carrier dynamics of the heavy-fermion metal CeCoIn5 probed by THz spectroscopy

• High-quality thin films of CeCoIn5 are prepared by molecular beam epitaxy.
• THz transmittance of thin-film CeCoIn5 was measured in heavy-fermion regime.
• Low-temperature THz response of CeCoIn5 cannot be described by simple Drude approach.

We discuss the charge carrier dynamics of the heavy-fermion compound CeCoIn5 in the metallic regime measured by means of quasi-optical THz spectroscopy. The transmittance of electromagnetic radiation through a CeCoIn5 thin film on a dielectric substrate is analyzed in the single-particle Drude framework. We discuss the temperature dependence of the electronic properties, such as the scattering time and dc-conductivity and compare with transport measurements of the sheet resistance. Towards low temperatures, we find an increasing mismatch between the results from transport and Drude-analyzed optical measurements and a growing incapability of the simple single-particle picture describing the charge dynamics, likely caused by the evolving heavy-fermion nature of the correlated electron system.