Far-infrared determination of scattering behavior and plasma frequency inV3Si,Nb3Ge, and Nb

Far-infrared transmission through normal-state films of ${\mathrm{V}}_3$Si, ${\mathrm{Nb}}_3$Ge, and Nb has been measured between 30 and 310 ${\mathrm{cm}}^{\mathrm{-}1}$. The data for ${\mathrm{V}}_3$Si followed the Drude model at low frequencies with constant scattering time and plasma frequency, but led to frequency-dependent Drude parameters above 150–240 ${\mathrm{cm}}^{\mathrm{-}1}$. This behavior is interpreted as arising from electron-phonon and impurity scattering effects, with the latter exhibiting a frequency dependence due to the variable electronic density of states. ${\mathrm{Nb}}_3$Ge also displayed high-frequency deviations from the Drude model whereas Nb did not. These characteristics are consistent with the electron-phonon behavior of each material. For ${\mathrm{V}}_3$Si, ${\mathrm{Nb}}_3$Ge, and Nb, respectively, the impurity scattering times were found to be 3.7×${10}^{\mathrm{-}14}$, 0.7×${10}^{\mathrm{-}14}$, and 1.0×${10}^{\mathrm{-}14}$ sec and the bare plasma frequencies were determined as 2.9, 4.0, and 10 eV.