Temperature dependence of low-energy optical conductivity of Yb-4(As1-xPx)(3) (x=0, 0.05, 0.15)

To investigate the anomalous transport property and the electronic structur e near the Fermi level of Yb4As3, we measured the temperature dependence of the reflectivity spectra of Yb-4(As1-xPx)(3) (x = 0, 0.05, 0.15) in the ph oton energy range of 2 meV-1.5 eV. The optical conductivity spectrum due to carrier absorption (Drude curve) significantly changes with temperature. A bove 200 K, the Drude curve with a high effective carrier density (N-eff) a nd a short relaxation time (tau) is commonly observed in all Yb-4(As1-xPx)( 3). On the other hand, below 70 K, the Drude curve changes to one with a lo w N-eff and a long tau below 10 meV. At the same temperature, a new peak ap pears at 15 meV in Yb4As3. The Drude curve and the new peak are considered to originate from the bare As 4p hole band and the hybridization state betw een the 4f and 5d bands on the Yb3+ chain, respectively.