Controlled atomic defects in the resulting films narrowly explain the emergence of superconductivity

An international team led by MPI-CPF researchers used irradiation with ultra-high-energy electrons to control atomic defects in superconducting nickelate thin films. Their systematic investigations have recently been published Physical review letters helps narrow down possible answers to fundamental questions about how superconductivity emerges in these materials.

Superconductors are materials that completely eliminate magnetic fields and transmit electric currents completely without loss, properties that make them exciting playgrounds for both the fundamental physical understanding of materials as well as the investigation of potentially revolutionary technological building blocks.

Some types of superconductors are relatively well understood, defined by theoretical models developed in the 1950s. Other classes of superconductors remain more mysterious, but can exhibit superconductivity at high 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 Zurich. Prior to this revolutionary work, his initial efforts led to the search for superconductivity in closely related nickel-oxide compounds, which remained the subject of active work worldwide for decades until Stanford University researchers finally demonstrated nickelate superconductivity in 2019.

Nickelate superconductivity has rapidly emerged as a dynamic field with new compounds reaching high transition temperatures and showing striking similarities and interesting differences to their cuprate counterparts. Despite this progress, several important questions remain difficult to resolve.

Since the early days of discovery, research groups around the world have devoted enormous effort to improving the quality of nickel oxide (nickelate) materials as superconductors. Now, MPI-CPF researchers have collaborated with groups from Stanford University and Ecole Polytechnique to do the opposite. Starting with some of the best samples available, exposure to megavolt-energy electrons gradually introduces atomic-scale defects into the sample, gradually lowering the temperature at which they superconduct.

Different types of superconductors are more or less sensitive to such disorder in the atomic lattice, so systematic measurements with increasing defect densities allowed them to distinguish between the various proposed models of the superconducting mechanism and narrow down the possibilities.

This study deepens the understanding of how superconductivity emerges in nickels, particularly with respect to cuprates. It also lays the groundwork for future, more detailed research into a wider range of nickelate superconductors, and highlights key benchmarks for improving methods of making these materials.