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TT: Fachverband Tiefe Temperaturen

TT 53: Correlated Electrons: Heavy Fermions

TT 53.9: Talk

Thursday, March 14, 2013, 11:45–12:00, H19

Optical study of archetypical valence-fluctuating Eu systems — V. Guritanu¹, S. Seiro¹, •J. Sichelschmidt¹, N. Caroca-Canales¹, T. Iizuka², S. Kimura², C. Geibel¹, and F. Steglich¹ — ¹MPI Chemische Physik fester Stoffe, Dresden, Germany — ²UVSOR Facility, Institute for Molecular Science, Okazaki, Japan

We have investigated the optical conductivity of the prominent valence-fluctuating compounds EuIr₂Si₂ and EuNi₂P₂ in the infrared energy range to get new insights into the electronic properties of valence-fluctuating systems. For both compounds, we observe upon cooling the formation of a renormalized Drude response, a partial suppression of the optical conductivity below 100 meV and the appearance of a midinfrared peak at 0.15 eV for EuIr₂Si₂ and at 0.13 eV for EuNi₂P₂. Most remarkably, our results show a strong similarity with the optical spectra reported for many Ce- or Yb-based heavy-fermion metals and intermediate valence systems, although the phase diagrams and the temperature dependence of the valence differ strongly between Eu- and Ce-/Yb-systems. This suggests that the hybridization between 4f- and conduction electrons, which is responsible for the properties of Ce- and Yb-systems, plays an important role in valence-fluctuating Eu systems.