FAR INFRARED REFLECTIVITY OF Pr-DOPED YBa2Cu3O7 THIN FILMS

We report the room-temperature optical reflectivity on a set of Y 1-x Pr x Ba 2 Cu 3 O 7 thin films for x = G (Tc ≈ 90 K), x=0.3 (Tc≈50K), x = 0.4 (Tc = 35 K) and x = 0.5 (Tc ≈ 19 K), in the 30-22000 cm -1 frequency range. The Pr concentration dependences of phonons features were studied. From the reflectivity, we obtain the real part of the frequency dependent optical conductivity σ((ω) by Kramers-Kronig transformation (TKK). We find that the plasma frequency decreases with the increase of Pr content (x). This variation is consistent with the higher dc resistivity. We discuss the implication of these results for the understanding of both transport phenomena and pairing mechanism in high-Tc superconductor thin films.