Scientists in China have reported nickel-based high-temperature superconductors reaching transition temperatures of 63 K, 50 K, and 46 K under ambient pressure.

Published in Nature, the study by Xue Qikun’s team at the Southern University of Science and Technology, in collaboration with the University of Science and Technology of China, details the increase of a bilayer nickel-based material’s transition temperature to 63 K from a previous 45 K. 

The researchers also created two artificial structures with transition temperatures of 50 K and 46 K.

Operating at ambient pressure distinguishes these findings from previous nickel-based superconductivity research that often required high-pressure environments. 

The team first engineered specific atomic stacking sequences and then identified nickel-based materials as a third class of high-temperature superconductors, following copper- and iron-based systems. 

This progress addresses the requirement for high oxidation states, which typically makes material growth unstable under conditions that allow for superconductivity.

Managing material growth at atomic scale

The team used a technique called strong oxidation atomic-layer epitaxy to manage material growth at the atomic scale. This method enables the layer-by-layer assembly of atomic structures under extreme oxidation conditions. 

By controlling growth in this manner, the researchers produced high-quality nickel oxide films with specific electronic properties, as reported by CGTN. 

Beyond material synthesis, the team identified electronic features associated with these states to better understand the underlying physics.

Using angle-resolved photoemission spectroscopy, the researchers found that superconducting samples share a distinct electronic band structure near the Fermi surface. This could be surmised as experimental evidence for the physical mechanism of the materials. 

The findings establish a link between atomic structure, electronic behavior, and superconductivity, which helps define the properties and behaviors of high-temperature superconductors.

Comparative studies of nickel-, copper-, and iron-based materials are intended to help solve the mechanisms of high-temperature superconductivity. Understanding these processes is relevant to the development of energy transmission systems, precision sensors, and quantum computing. 

Applicable to future energy technologies

Designing materials at the atomic level offers a method for creating systems that allow electrical current to flow without resistance, which is applicable to future energy and information technologies.

In a separate development, researchers have analyzed thin films of the material La3Ni2O7 to determine how superconductivity emerges in this family of compounds.

“A key piece of the puzzle was missing: the phase diagram. We wanted to see if this bilayer system has a ‘superconducting dome’—the classic hallmark of unconventional high-Tc superconductors,” explained Yuefeng Nie, one of the study authors and a professor at Nanjing University, at that time.

After measuring the material’s properties, the scientists constructed a phase diagram that revealed a superconducting dome. This is a curved region where superconductivity appears and strengthens under specific conditions. 

The presence of this dome is similar to patterns seen in electron-doped copper-based superconductors, or cuprates. This similarity suggests that superconductivity in nickelates may be related to Fermi surface reconstruction and electronic symmetry.

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