Chinese scientists develop nickelate high-temperature superconductors at ambient pressure

SHENZHEN, Feb. 18 (Xinhua) -- A joint research team from Southern University of Science and Technology (SUSTech) and other Chinese institutions has developed a new type of high-temperature superconductors at ambient pressure, achieving a breakthrough in superconductivity research.

According to a research paper published on Tuesday in the journal Nature, a team consisting of members from SUSTech, the Quantum Science Center of the Guangdong-Hong Kong-Macao Greater Bay Area, and Tsinghua University reported nickelate superconductivity under ambient pressure, with an onset transition temperature that exceeds 40 K, which is about minus 233 degrees Celsius, alongside the existence of definitive evidence of zero electrical resistance and the expulsion of magnetic fields.

This discovery establishes nickelate materials as the third class of high-temperature superconductors, following cuprates and iron-based systems, capable of operating in ambient conditions. This study also sheds light on the enigma of high-temperature superconductivity mechanisms.

Superconductivity is renowned for its zero-resistance electrical conduction and has captivated the attention of scientists since its discovery in 1911. The highest transition temperature of conventional superconductors is 40 K, also known as the McMillan limit. The search for superconducting materials with higher transition temperatures has become a key quest in the scientific community.

Previous discoveries of cuprate superconductors and iron-based superconductors, which operate above the McMillan limit, established the high-temperature superconductor family -- but their underlying mechanisms still remain unresolved.

Initial studies in 2019 revealed superconductivity in infinite-layer nickelate films, though at temperatures much lower than 40 K. A study in 2023, led by Chinese scientists, achieved superconductivity in bilayer nickelates under pressures exceeding 100,000 atmospheres.

Since then, realizing high-temperature superconductivity under ambient conditions has become a major goal for researchers worldwide.

The team led by Xue Qikun, an academician of the Chinese Academy of Sciences, and Chen Zhuoyu, an SUSTech researcher, pioneered a new technique to enable atomic-scale layer-by-layer growth of oxide films under oxidative conditions 10,000 times stronger than conventional methods, allowing precise control over chemical composition to construct oxide films with high crystal quality.

This technique represents a leap forward in oxide epitaxy methodology, and not only resolves oxygen deficiency challenges in oxide materials, but also unlocks new potential for designing and developing related systems, such as high-temperature superconductors.

Notably, this method was applied in the development of nickelate superconductors. After testing more than 1,000 samples to overcome structural instability, the team finally developed the new type of high-temperature superconductors at ambient pressure.

The breakthrough also indicates that by using interface engineering for optimizing material design, there are promising prospects for achieving nickelate superconductivity at higher temperatures, including in the liquid nitrogen temperature range between minus 210 to minus 196 degrees Celsius, according to the study. ■