Researchers achieve 40 K superconductivity with high fields, overcoming magnetic suppression effects

Superconductivity, the ability of a material to conduct electricity with zero resistance, is typically weakened by strong magnetic fields, but recent research demonstrates a surprising reversal of this effect in a promising class of high-temperature superconductors. Km Rubi, of the National High Magnetic Field Laboratory and Los Alamos National Laboratory, alongside King Yau Yip and Elizabeth Krenkel from the National University of Singapore and Los Alamos National Laboratory, and their colleagues, reveal that intense magnetic fields can actually boost superconductivity in infinite-layer nickelates, materials capable of sustaining this state at temperatures up to 40 Kelvin. This discovery challenges conventional understanding, as most materials exhibiting magnetic-field-induced superconductivity possess very low transition temperatures, and suggests a pathway towards significantly enhancing the upper limits of magnetic fields that these materials can withstand while remaining superconducting. The team’s findings, rooted in a mechanism similar to the Jaccarino-Peter effect, open new avenues for developing more robust and practical high-temperature superconducting technologies.

Magnetic fields typically suppress superconductivity, but rare materials, including certain nickelates and organic conductors, exhibit superconductivity even in strong magnetic fields. These materials generally have low superconducting transition temperatures, and the mechanisms driving this unusual behaviour remain poorly understood. The team observed a re-entrant superconducting state at very low temperatures and high fields, where superconductivity reappears after initial suppression, and the upper critical field did not saturate, even at the highest fields tested. Detailed analysis confirmed the films’ structural quality, while electrical transport measurements revealed the unusual superconducting behaviour. These findings challenge conventional understanding of superconductivity and open up possibilities for new technologies.

Tunable Superconductivity in Infinite-Layer Nickelate

A novel nickelate material, designated (SECS)NiO2, exhibits remarkably enhanced superconductivity at temperatures as high as 40 Kelvin, significantly exceeding the performance of previously known reentrant superconductors. The material possesses two distinct superconducting phases, tunable by manipulating the orientation of an applied magnetic field, and a robust high-field superconducting state. The upper critical field displays a sharp increase, not saturating even at 60 Tesla, and theoretical modeling confirms a substantial exchange field contributing to the enhanced robustness of the superconducting state. This exchange field arises from interactions between conduction electrons and localized rare-earth moments, a feature largely absent in other high-temperature superconductors, and the material’s unique electronic structure suppresses magnetic ordering, creating a more favorable environment for superconductivity. Increasing the magnetic field induces a new superconducting state at high fields, explained by a compensation mechanism, and the material exhibits extraordinarily large upper critical fields, exceeding 65 Tesla, indicating a remarkable resilience to magnetic fields. These findings suggest that nickelates possess considerable potential for applications requiring high magnetic fields, such as superconducting magnets and sensitive quantum magnetometers, and further research is needed to fully understand the underlying mechanisms and refine material composition.