Optical study of archetypical valence-fluctuating Eu systems.


We have investigated the optical conductivity of the prominent valence-fluctuating compounds EuIr(2)Si(2) and EuNi(2)P(2) 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 EuIr(2)Si(2) and 0.13 eV for EuNi(2)P(2). 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 systems and Ce- or Yb-based 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.

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@article{Guritanu2012OpticalSO, title={Optical study of archetypical valence-fluctuating Eu systems.}, author={V Guritanu and Silvia Seiro and J . Sichelschmidt and Nubia Caroca-Canales and Takuya Iizuka and S-i Kimura and C Geibel and Frank Steglich}, journal={Physical review letters}, year={2012}, volume={109 24}, pages={247207} }