The superconducting gap of an ultrathin nickelate defies expectations

Superconductors are materials that carry electrical current with zero resistance below a specific critical temperature. In conventional superconductors, the transition to superconductivity generally occurs at very low temperatures.

This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Add as preferred source Nature Physics (2026)"> Electronic structure and nodeless superconducting gap of the bilayer nickelate thin film.

Credit: Wenjie Sun et al, Nature Physics (2026) Superconductors are materials that carry electrical current with zero resistance below a specific critical temperature. Researchers at Nanjing University, the University of Science and Technology of China, the Hong Kong Polytechnic University and other institutes in China recently investigated the electronic processes underpinning superconductivity in La₃Ni₂O₇, a nickelate that has exhibited.

The evidence they collected, published in Nature Physics, suggests that superconductivity in specially engineered La₃Ni₂O₇-based films could arise from an electron-pairing mechanism distinct from the d-wave pairing associated with cuprate superconductors. Unlike cuprates, where the low-energy physics is largely governed by a single Cu 3dₓ²₋ᵧ² orbital with a d⁹ electronic configuration, bilayer nickelates feature a d⁷‧⁵ configuration where both Ni 3dₓ²₋ᵧ² and 3dᶻ² orbitals sit close to the Fermi level.

This multiband nature raises fundamental questions regarding the pairing mechanism, sparking extensive theoretical and experimental debate. " The researchers wanted to better understand how superconductivity emerges in bilayer nickelates. First, does the Ni 3d z 2 -dominated γ band actually cross the Fermi level, and what is its role in superconductivity?" said Prof.

Our close collaboration began here, combining Nanjing University's high-quality molecular-beam epitaxy (MBE) growth with the state-of-the-art micro-ARPES BL-03U beamline at Shanghai Synchrotron Radiation Facility (SSRF) built by our group.

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