Induction of superconductivity in Y0.4Pr0.6Ba2-xSrxCu3O7 system with increasing Sr substitution

TL;DR

This study demonstrates that increasing Sr substitution in Y0.4Pr0.6Ba2-xSrxCu3O7 induces a transition from semiconducting to superconducting behavior, revealing insights into the role of structural and electronic modifications in high-temperature superconductivity.

Contribution

It provides new evidence that Sr substitution enhances metallicity and superconductivity in Pr-doped YBCO compounds by reducing Pr hybridization and disorder.

Findings

Superconductivity appears at x=0.80 and 1.00 with Tc around 5 and 14 K.

Resistivity ratio decreases with increasing Sr content, indicating increased metallicity.

Room temperature thermoelectric power decreases with Sr substitution, implying more mobile holes.

Abstract

Samples of Y0.4Pr0.6Ba2-xSrxCu3O7 have been synthesized by a solid- state reaction route. The samples with x = 0.60 crystallize in an orthorhombic structure (with orthorhombic distortion decreasing with increasing x), while the samples with x=0.80 and 1.0 crystallize in a pseudo tetragonal structure. Resistance (R) measurements as a function of temperature (T) show that x = 0.0 sample is highly semiconducting with R2K/R300K ratio of ~ 65. This ratio decreases to only ~23 and 5 for x=0.20 and x=0.4 samples, respectively. Further, the x=0.60 sample shows onset of a broad superconducting transition temperature (Tconset) at around 20 K without achieving the TcR=0 state down to 2 K. The TcR=0 state is observed in x = 0.80 and 1.00 samples at around 5 and 14 K, respectively. Thermo-electric power (S), also exhibits TcS~0 state at around 11 K and 16 K, respectively for x = 0.8 and 1.00 samples. Thermo electric power at room temperature is positive and decreases with increasing x, indicating enhanced number of mobile holes. These results demonstrate that substitution of Sr at Ba-site systematically induces metallicity and eventually superconductivity in Y0.4Pr0.6Ba2-xSrxCu3O7 system. The results are explained on the basis of reduced Pr(4f) orbital hybridization with O(2p) in supercondu cting Cu-O2 planes, resulting in delocalization of the mobile carriers. The role of decreased Pr/Ba intermixing disorder is also considered.