Probing the Fermi level of Y1-xPrxBa2Cu3O7-δ by femtosecond spectroscopy

Abstract Femtosecond spectroscopy at room temperature indicates a monotonic rise in the Fermi level E F vs. Pr concentration x in Y 1-x Pr x Ba 2 Cu 3 O 7-δ . For x=0.12±0.02, the Fermi level lies 2.0 eV below the unoccupied Cu d bands. The decrease in T c with increasing x is consistent with a band filling model. The room temperature decay time τ of the transient reflectivity ΔR increases from τ 2 Cu 3 O 7-δ to τ =140 fs in non-superconducting PrBa 2 Cu 3 O 7-δ . The effects of Pr substitution for Y on the position of the Fermi level are qualitatively similar to the effects of de-oxygenation on the E F of YBa 2 Cu 3 O 7-δ .