Universal scaling in the dynamical conductivity of heavy fermion Ce and   Yb compounds
  Dynamical conductivity spectra s(w) have been measured for a diverse range of heavy-fermion (HF) Ce and Yb compounds. A characteristic excitation peak has been observed in the mid-infrared region of s(w) for all the compounds, and has been analyzed in terms of a simple model based on conduction (c)-f electron hybridized band. A universal scaling is found between the observed peak energies and the estimated c-f hybridization strengths of these HF compounds. This scaling demonstrates that the model of c-f hybridized band can generally and quantitatively describe the charge excitation spectra of a wide range of HF compounds. 
H. Okamura, T. Watanabe, M. Matsunami, T. Nishihara, N. Tsujii, T.   Ebihara, H. Sugawara, H. Sato, Y. Onuki, Y. Isikakwa, T...