Reduction dependence of superconductivity in undoped T' cuprates

TL;DR

This study explores how the reduction process affects superconductivity in undoped T'-RE2CuO4 thin films, emphasizing the importance of oxygen removal and lattice constant as indicators for optimal superconducting properties.

Contribution

It introduces a method to evaluate reduction quality via c-axis lattice constant, aiding in optimizing superconductivity in undoped T'-RE2CuO4 films.

Findings

Superconductivity in undoped T'-RE2CuO4 is achieved through careful reduction.

The c-axis lattice constant correlates with the reduction level and superconducting quality.

Optimal reduction minimizes impurity oxygen atoms, enhancing superconductivity.

Abstract

We have recently achieved superconductivity in undoped T'-RE2CuO4 (RE: Pr, Nd, Sm, Eu, and Gd), using epitaxial thin films by metal organic decomposition. The key recipes to achieve superconductivity are low-PO2 firing and subsequent vacuum reduction to minimize the amount of impurity oxygen atoms, which are very harmful to high-Tc superconductivity. In this article, we report our investigation on the reduction dependence of superconductivity of T'-RE2CuO4. For thin films, the amount of remnant Oap atoms is difficult to evaluate but we propose that one good measure for this may be the c-axis lattice constant, which tells us whether the reduction is insufficient or excessive.