Out of plane effect on the superconductivity of Sr2-xBaxCuO3+y with Tc up to 98K

TL;DR

This study shows that substituting Ba into Sr2CuO3+y enhances its superconducting transition temperature up to 98K by optimizing local geometric structure, surpassing previous records and highlighting the importance of out-of-plane effects.

Contribution

It demonstrates that out-of-plane structural modifications, specifically Ba substitution, can significantly increase Tc in cuprate superconductors beyond disorder effects.

Findings

Tc reaches 98K at x=0.6 Ba substitution.

Superconductivity is influenced by apical oxygen order and Ba content.

Out-of-plane structural effects can dramatically enhance Tc.

Abstract

A series of new Sr2-xBaxCuO3+y (0 x 0.6) superconductors were prepared using high-pressure and high-temperature synthesis. A Rietveld refinement based on powder x-ray diffraction confirms that the superconductors crystallize in the K2NiF4-type structure of a space group I4/mmm similar to that of La2CuO4 but with partially occupied apical oxygen sites. It is found that the superconducting transition temperature Tc of this Ba substituted Sr2CuO3+y superconductor with constant carrier doping level, i.e., constant d, is controlled not only by order/disorder of apical-O atoms but also by Ba content. Tcmax =98 K is achieved in the material with x=0.6 that reaches the record value of Tc among the single-layer copper oxide superconductors, and is higher than Tc=95K of Sr2CuO3+y with optimally ordered apical-O atoms. There is Sr-site disorder in Sr2-xBaxCuO3+y which might lead to a reduction of Tc. The result indicates that another effect surpasses the disorder effect that is related either to the increased in-plane Cu-O bond length or to elongated apical-O distance due to Ba substitution with larger cation size. The present experiment demonstrates that the optimization of local geometry out of the Cu-O plane can dramatically enhance Tc in the cuprate superconductors.