New measurements of nickelate superconductors reveal clues about their hidden electronic behavior.
The mechanism behind high-temperature (TC) superconductivity remains one of condensed matter physics’ major unsolved problems. Chinese researchers have now made important progress in studying high-TC nickelate superconductors.
For the first time, scientists identified a nodeless superconducting gap and detected electron-boson coupling by examining the electronic structures of Ruddlesden-Popper bilayer nickelate superconducting thin films. The findings offer important evidence related to two central questions in high-TC nickelates: “superconducting gap symmetry” and “superconducting pairing mechanism.”
The study was led by Junfeng He of the University of Science and Technology of China (USTC), part of the Chinese Academy of Sciences, in collaboration with teams led by Qikun Xue and Zhuoyu Chen of the Southern University of Science and Technology (SUSTech). It was published in Science on May 21, 2026.
Searching for the Superconducting Gap
Superconductivity, discovered in 1911, is known for its unusual electromagnetic properties and has become a major focus of physics research. Over the past century, scientists have discovered copper-based and iron-based high-TC superconductors, but the mechanism behind high-TC superconductivity is still not fully understood. Nickel-based high-TC superconductors (nickelates) offer a new way to investigate the problem.
In high-TC superconductors, “superconducting gap symmetry” is considered a key clue to how superconductivity works. One especially important question is whether the superconducting gap contains “nodes” (points where the superconducting gap is zero) in momentum space. Using angle-resolved photoemission spectroscopy (ARPES), the team studied Ruddlesden-Popper bilayer nickelate superconducting thin films. They found no gap nodes anywhere in momentum space, a result consistent with s-wave (s±) superconducting gap symmetry.
Evidence of Electron-Boson Coupling
Another major question is how “electron pairs” form in high-TC superconductors. In theory, electrons can pair through “electron-boson coupling.” The researchers observed a dispersion kink about 70 meV below the Fermi level, which is a “finger print” of electron-boson coupling. This provides important evidence for understanding how electron pairing may occur.
In the collaboration, the SUSTech team led the thin film growth, while the USTC team performed the electronic structure measurements. To prevent oxygen loss during sample transfer, the researchers developed a method based on liquid-nitrogen-cooled ultra-high vacuum low-temperature sample quenching and transfer. This approach allowed samples to be moved successfully from Shenzhen to Hefei and helped make the experiments possible.
Reference: “Nodeless superconducting gap and electron-boson coupling in (La,Pr,Sm)3Ni2O7 films” by Jianchang Shen, Guangdi Zhou, Yu Miao, Peng Li, Zhipeng Ou, Yaqi Chen, Zechao Wang, Runqing Luan, Hongxu Sun, Zikun Feng, Xinru Yong, Yueying Li, Lizhi Xu, Wei Lv, Zihao Nie, Heng Wang, Haoliang Huang, Yu-Jie Sun, Qi-Kun Xue, Junfeng He and Zhuoyu Chen, 21 May 2026, Science.
DOI: 10.1126/science.adw8329
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Full article can be found at: https://scitechdaily.com/scientists-crack-key-mystery-behind-high-temperature-superconductors/
