Microscopic annealing process and its impact on superconductivity in T'-structure electron-doped copper oxides

TL;DR

This paper investigates how microscopic oxygen reduction during annealing repairs copper deficiencies and creates oxygen vacancies in electron-doped copper oxides, revealing a common mechanism for superconductivity in both electron- and hole-doped cuprates.

Contribution

It uncovers the microscopic process of oxygen reduction in electron-doped cuprates and its role in inducing superconductivity, resolving a long-standing materials issue.

Findings

Oxygen reduction repairs Cu deficiencies.

Oxygen vacancies create itinerant carriers.

Superconductivity mechanism is similar for electron- and hole-doped cuprates.

Abstract

High-transition-temperature superconductivity arises in copper oxides when holes or electrons are doped into the CuO2 planes of their insulating parent compounds. While hole-doping quickly induces metallic behavior and superconductivity in many cuprates, electron-doping alone is insufficient in materials such as R2CuO4 (R is Nd, Pr, La, Ce, etc.), where it is necessary to anneal an as-grown sample in a low-oxygen environment to remove a tiny amount of oxygen in order to induce superconductivity. Here we show that the microscopic process of oxygen reduction repairs Cu deficiencies in the as-grown materials and creates oxygen vacancies in the stoichiometric CuO2 planes, effectively reducing disorder and providing itinerant carriers for superconductivity. The resolution of this long-standing materials issue suggests that the fundamental mechanism for superconductivity is the same for electron- and hole-doped copper oxides.