Recently, a joint research team led by Prof. Zhang Junjie and Prof. Tao Xutang from the State Key Laboratory of Crystal Materials, Shandong University, has achieved a breakthrough in nickelate high-temperature superconductors. The team includes researchers from multiple renowned institutions, including Prof. Zeng Qiaoshi at the Center for High Pressure Science and Technology Advanced Research, Prof. Zhou Rui at the Institute of Physics, Chinese Academy of Sciences, Prof. Zheng Qiang at the National Center for Nanoscience and Technology, and Prof. Chen Yusheng at the University of Chicago. The paper entitled “Bulk Superconductivity Up to 96 K in Pressurized Nickelate Single Crystals” has published online in the prestigious journal Nature on Dec. 2, 2025.

First authors of the paper are PhD student Li Feiyu at the State Key Laboratory of Crystal Materials, Shandong University, and PhD student Xing Zhenfang at the Center for High Pressure Science and Technology Advanced Research. Corresponding authors are Prof. Zhang Junjie and Prof. Tao Xutang at Shandong University, and Prof. Zeng Qiaoshi and Dr. Peng Di at the Center for High Pressure Science and Technology Advanced Research. The State Key Laboratory of Crystal Materials, Shandong University, is the leading corresponding institution for this research.

Two long-standing fundamental questions in nickelate superconductivity. High-temperature superconductivity has attracted much attention due to their potential applications in energy, information, medical, and transportation etc. However, the origin of high-temperature superconductivity remains a big challenge, which is listed by the journal Science as one of the "125 key scientific problems that human has not yet solved". Nickelate superconductors are a new class of high-temperature superconductors discovered in 2019 by scientists at Stanford University. Despite intense research, they still exist two key fundamental questions: (1) The observation of bulk high temperature superconductivity requires two "high pressure" conditions: single crystal growth from high pressure oxygen floating zone growth and high-pressure measurements. Of particular importance is that is it possible to remove the two high-pressure conditions? (2) For all known nickelate superconductors, the maximum superconducting transition temperature (T_c) remains at ~80 K for more than two years, which is much lower than the 164 K of cuprate superconductors. Design and synthesis of higher Tc nickelate superconductors remain a grand challenge.

Ambient-pressure flux growth removes the “high pressure” synthesis requirement. The research team pioneered the ambient-pressure flux method for superconducting nickelate single crystals, an approach that uses K₂CO₃ as the flux. Through this innovative technique, the team successfully grew a series of bilayer nickelate single crystals at ambient pressure. Comprehensive characterization confirmed that these single crystals are of high quality. This achievement solves the "bottleneck problem" in the preparation of high-quality nickelate superconducting single crystals.

Applying chemical pressure strategy to achieve record high (96 K) superconducting transition temperature in nickelates. The team found that La₂SmNi₂O₇ exhibits clear bulk high temperature superconductivity: (1) Zero resistivity. Resistivity measurements at 21.6 GPa show T_c,max^onset = 92 K with zero resistivity at 73 K, which is the highest among all known nickelate superconductors; (2) Meissner effect. Magnetic susceptibility measurements at 20.6 GPa reveal Meissner effect at 60 K with a superconducting volume fraction exceeding 60%. High pressure low temperature structural study revealed that both monoclinic and tetragonal crystal structures support superconductivity. Through detailed structural analysis, the team found a correlation between larger ambient-pressure structural distortion Δ=(a-b)/(a+b) and higher T_c,max under high pressure. Guided by this strategy, the team further discovered that La_1.57Sm_1.43Ni₂O_7-δ single crystals show T_c,max up to 96 K (approximately -177 ℃) under high pressure, which sets a new world record for the nickel-based superconductors.

In sum, the team's newly developed "ambient-pressure flux growth method" completely removes the reliance on high-pressure conditions for single crystal growth, and provides a low-cost and easy-to-access solution for high-quality nickelate superconducting single crystals. In addition, the "lattice distortion-T_c" strategy offers an effective path for achieving higher T_c nickelate high-temperature superconductors.

This research was supported by the National Natural Science Foundation of China, the Taishan Scholar of Shandong Province, State Key Laboratory of Crystal Materials, Shandong University, the National Key Research and Development Projects of China, Shanghai Key Laboratory of Advanced Materials in Extreme Conditions, and the Shanghai Science and Technology Committee, China. The research also used facilities including Synergetic Extreme Condition User Facility (SECUF), BL17UM Beamline of Shanghai Synchrotron Radiation Facility (SSRF), and BL10XU Beamline of Spring-8.