Disorder on demand

Controllably suppressing superconductivity in nickelate thin films provides insights for their pairing symmetry

To the point

• Superconductivity: An international team led of researchers at MPICPfS used high-energy electron irradiation to introduce atomic defects in nickelate thin films, providing insights into superconductivity.
• Understanding Mechanisms: The study helps clarify how superconductivity emerges in nickelates compared to cuprates and narrows down models explaining these mechanisms.
• Future Research: Findings pave the way for more comprehensive studies on nickelate superconductors and set benchmarks for enhancing material production.

Superconductors are materials that completely expel magnetic fields and perfectly transmit electrical current without any losses, properties which make them both fascinating playgrounds to probe fundamental physical understanding of materials as well as potentially revolutionary technological building blocks. Some kinds of superconductors are relatively well-understood, explained by theoretical models developed starting in the 1950s. Other classes of superconductors remain more mysterious, but can exhibit superconductivity at higher temperatures, making them more attractive for practical applications.

The most famous of these “unconventional” superconductors are copper-oxide ceramics, or cuprates, first discovered in 1986 by researchers at IBM Zürich. Prior to that revolutionary work, their early efforts started the search for superconductivity in closely related nickel-oxide compounds, which remained a subject of active work around the world for decades until nickelate superconductivity was finally demonstrated by researchers at Stanford University in 2019. Nickelate superconductivity has rapidly emerged as a vibrant field with new compounds reaching higher transition temperatures and revealing both striking similarities and intriguing differences to their cuprate counterparts. Despite this progress, several key questions remain difficult to resolve – largely due to the complex and highly precise synthesis techniques required to produce these superconducting nickelates.

From the early days of discovery, research groups around the world have invested immense effort in improving the quality of superconducting nickel oxide (nickelate) materials. Now, researchers at MPI-CPfS have collaborated with groups at Stanford University and Ecole Polytechnique to do the opposite: starting with some of the best samples available, exposure to megavolt energy electrons slowly introduces atomic-scale defects into the samples, gradually reducing the temperature at which they superconduct. Different kinds of superconductors are more or less sensitive to this kind of disorder in the atomic lattice, so systematic measurements with increasing defect densities allowed them to distinguish between various proposed models of the superconducting mechanism and narrow down the possibilities.

This study - just published  in Physical Review Letters  helps deepen our understanding of how superconductivity emerges in nickelates, particularly in relation to that of cuprates. It also lays the groundwork for more detailed future research across a wider range of nickelate superconductors, and highlights key benchmarks for improving how these materials are made.