Terahertz Conductivity of the Heavy-Fermion State in CeCoIn5

TL;DR

This study investigates the terahertz optical conductivity of CeCoIn5 thin films, revealing heavy-fermion electrodynamics with a temperature-dependent relaxation rate and a gradually evolving coherent state.

Contribution

First measurement of terahertz conductivity in CeCoIn5 thin films showing heavy-fermion behavior and temperature-dependent relaxation dynamics.

Findings

Drude-like conductivity observed at terahertz frequencies.

Relaxation rate increases linearly with temperature.

Coherent heavy-fermion state develops gradually upon cooling.

Abstract

The optical properties of thin films of the heavy-fermion compound CeCoIn5, which were deposited by molecular beam epitaxy onto MgF2 substrates, have been studied at frequencies 7 to 45 cm^{-1} (corresponding to 0.2 to 1.3 THz) and temperatures 2 to 300 K. We observe an electrodynamic behavior which is typical for heavy fermions, namely Drude-like conductivity with a relaxation rate at rather low frequencies. This relaxation rate increases almost linearly with temperature up to at least 30 K. The coherent heavy-fermion state, characterized by an increase of the effective mass, continuously evolves upon cooling and is not fully developed for temperatures as low as 5 K.