Evolution and Control of Oxygen Order in a Cuprate Superconductor

TL;DR

This study demonstrates how defect ordering, manipulated by X-ray irradiation, can control superconductivity in La2CuO4+y, revealing a direct link between oxygen intercalant order and high-quality superconducting regions.

Contribution

It introduces a novel X-ray writing technique to induce and study oxygen defect order in a cuprate superconductor, correlating defect order with superconducting properties.

Findings

Ordered regions grow after irradiation and are linked to enhanced superconductivity.

Oxygen intercalant order exhibits a unique anisotropy evolution during growth.

High-quality superconductivity is associated with two-dimensional defect ordering.

Abstract

The disposition of defects in metal oxides is a key attribute exploited for applications from fuel cells and catalysts to superconducting devices and memristors. The most typical defects are mobile excess oxygens and oxygen vacancies, and can be manipulated by a variety of thermal protocols as well as optical and dc electric fields. Here we report the X-ray writing of high-qualitysuperconducting regions, derived from defect ordering, in the superoxygenated layered cuprate, La2CuO4+y. Irradiation of a poor superconductor prepared by rapid thermal quenching results first in growth of ordered regions, with an enhancement of superconductivity becoming visible only after a waiting time, as is characteristic of other systems such as ferroelectrics, where strain must be accommodated for order to become extended. However, in La2CuO4+y, we are able to resolve all aspects of the growth of (oxygen) intercalant order, including an extraordinary excursion from low to high and back to low anisotropy of the ordered regions. We can also clearly associate the onset of high quality superconductivity with defect ordering in two dimensions. Additional experiments with small beams demonstrate a photoresist-free, single-step strategy for writing functional materials.