Effect of chemical inhomogeneity in bismuth-based copper oxide superconductors

Abstract

We examine the effect on the superconducting transition temperature (Tc) of chemical inhomogeneities in Bi2Sr2CuO 6+δ and Bi2Sr2CaCu2O 8+δ single crystals. Cation disorder at the Sr crystallographic site is inherent in these materials and strongly affects the value of Tc. Partial substitution of Sr by Ln (Ln = La, Pr, Nd, Sm, Eu, Gd, and Bi) in Bi2Sr1.6Ln0.4CuO 6+δ results in a monotonic decrease of Tc with increasing ionic radius mismatch. By minimizing Sr site disorder at the expense of Ca site disorder, we demonstrate that the Tc of Bi2Sr2CaCu2O 8+δ can be increased to 96 K. Based on these results we discuss the effects of chemical inhomogeneity in other bulk high-temperature superconductors.

A Universal Scaling Relation in High‐Temperature Superconductors.

“…Similarly, an attempt to scale λ with σ dc was only partially successful 8 . We demonstrate here that the simple relation ρ s ∝ σ dc T c , with σ dc measured at T ≅ T c , universally holds for all high-T c materials, regardless of doping level, crystal structure and type of disorder 9 , nature of dopant (electrons versus holes) and direction (parallel or perpendicular to the copper oxygen planes). Moreover, we show that this relation approximately holds for some conventional superconductors as well.…”

Electronically driven superconductor-insulator transition in electrostatically doped La2CuO4+δthin films

“…17 δ-LCO crystals are believed to be the simplest cuprate HTS since the i-O are not randomly distributed, and moreover, they have the highest T C since the i-O are located far away from the superconducting CuO 2 planes. 13,17 Unfortunately, in the study of the phase diagram of δ-LCO bulk compounds it is impossible to produce a series of doped samples in which the concentration of oxygen is systematically varied since the system exhibits phase separation over wide ranges of oxygen doping. 13 …”

Improvement of superconducting properties in Na-doped BSCCO superconductor

“…These substitutions lead to important changes in charge carrier concentration and also release the restriction of spin alignment due to the spin lattice interaction [23]. The effect of such changes is one of the important features that help understanding the structural details and superconducting properties along with the mechanism of occurrence of superconductivity [24][25][26]. Besides chemical doping, the production techniques have also been widely studied by researchers to produce high quality and homogeneous samples.…”