Abstract

Femtosecond spectroscopic measurements have been used to investigate a variety of physical phenomena in high-temperature superconductors, including electron-phonon coupling,¹ non-equilibrium superconductivity² and band-filling effects.³ In particular, as demonstrated by several groups,² time-resolved studies of undoped high-temperature superconductors have revealed qualitatively different dynamical responses when excited above and below the critical temperature. Here, we extend this work by examining the optical response of Pr_xY_1-xBa₂Cu₃O₇-δ for 0 < x < 0.25 in the temperature range 5 – 300 K. Pr doping of YBa₂Cu₃O_7-δ influences the superconducting properties in two related ways: first, it depresses the critical temperatures and eventually suppresses superconductivity^3,4 for x > 0.5; and second, it shifts the Fermi level upward by decreasing the hole concentration in the Cu-O planes while leaving the orthorhombic symmetry intact.⁴

© 1992 Optical Society of America