Abstract

Femtosecond time-resolved optical spectroscopy is an excellent experimental alternative to conventional spectroscopic methods that probe the low energy electronic structure in strongly correlated electron systems [1]. In particular, it has been shown that carrier relaxation dynamics are very sensitive to changes in the low energy density of states (e.g. associated with the formation of a low energy gap or pseudogap) providing new insights into the low energy electronic structure in these materials. In this report we present the first studies of carrier relaxation dynamics in heavy fermion (HF) systems by means of femtosecond time-resolved optical spectroscopy. Our results show that the carrier relaxation dynamics, below the Kondo temperature (T_K), are extremely sensitive to the low energy density of states (DOS) near the Fermi level to which localized f-moments contribute. Specifically, we have performed measurements of the photoinduced reflectivity ∆R/R dynamics as a function of temperature and excitation intensity on the series of HF compounds YbXCu₄ (X=Ag, Cd, In) [2] in comparison to their non-magnetic counterparts LuXCu₄.

© 2002 Optical Society of America