Superconducting materials, known for their zero electrical resistance and perfect diamagnetism, hold great potential in various fields such as energy, transportation, healthcare, and information technology. One of the key scientific challenges in this area is understanding the fundamental mechanism behind superconductivity.
In a recent study published in Science Advances, researchers from Nanjing University, the University of Science and Technology of China (USTC), and NYU Shanghai presented the first detailed mapping of the electronic band structure of infinite-layer nickelate superconductors. Their findings provide crucial experimental insights into the superconducting mechanism of this emerging material.
High-temperature superconducting cuprates remain one of the most important and widely studied superconductors. However, despite decades of research, their underlying superconducting mechanism is still not fully understood. In recent years, scientists discovered that nickelate superconductors share key similarities in electronic structure with cuprates, suggesting that they might follow a comparable superconducting mechanism. This makes nickelates a promising model system for exploring unconventional superconductivity and could lead to a deeper understanding of high-temperature superconductors.
One of the most fundamental properties governing superconductivity is the electronic band structure, which describes how electrons behave inside a material. Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool for probing this structure, but obtaining high-quality ARPES data requires exceptionally smooth sample surfaces. It’s particularly challenging to produce high-quality samples of the infinite-layer nickelates, as their surfaces are highly sensitive to degradation. Traditional generation methods often result in rough surfaces or unwanted chemical changes, making it difficult to prepare thin films suitable for ARPES measurements. As a result, the electronic structure of infinite-layer nickelates has remained elusive since their discovery.
In this study, researchers from Nanjing University and USTC successfully overcame this challenge by employing a self-developed atomic hydrogen reduction technique. This approach enabled them to produce high-quality infinite-layer nickelate thin films with pristine surfaces, allowing, for the first time, a precise ARPES measurement of the material’s electronic structure. Theoretical calculations, led by Associate Professor of Physics Chen Hanghui and his team at NYU Shanghai, closely matched the experimental data, further validating the proposed low-energy effective model.
The study reveals both similarities and differences between infinite-layer nickelates and cuprates. Both materials exhibit comparable electron interactions, movement patterns, and energy evolution characteristics. However, significant differences arise in their three-dimensional electronic structure, Fermi surface behavior, and specific electronic interactions. These findings provide new insights into the nature of nickelate superconductors and offer a fresh perspective on unconventional superconductivity.
The paper’s co-first authors are Sun Wenjie and Hao Bo from Nanjing University, Jiang Zhicheng from USTC, and postdoctoral research fellow Xia Chengliang from NYU Shanghai. Professors Nie Yuefeng (Nanjing University), Shen Dawei (USTC), and Chen Hanghui (NYU Shanghai) are the corresponding authors of the study.