A team from the Department of Physics at Fudan University discovered a new type of high-temperature superconductor, and the results were published in Nature

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2024-07-18 08:48Posted on the official account of Shanghai The Paper

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01Professor Zhao Jun's team from the Department of Physics of Fudan University published research results on new high-temperature superconductors in Nature.

02The team successfully synthesized a high-quality single crystal sample of La4Ni3O10, a three-layer nickel oxide, which confirmed the pressure-induced bulk superconductivity of nickel oxide.

03 The volume fraction of superconductivity reaches 86%, which is close to that of copper oxide high-temperature superconductors, which provides a new perspective and platform for people to understand the mechanism of high-temperature superconductivity.

04 In addition, these materials exhibit exotic metals and unique interlayer coupling behavior.

05Jun Zhao's team will continue to focus on major issues in the field of high-temperature superconductivity and explore the internal relationship and mechanism of high-temperature superconductors in different systems.

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Superconductors have attracted much attention due to their huge application potential, and the search for new high-temperature superconductors is the goal of the scientific community.

北京时间7月17日晚，复旦大学物理学系赵俊教授团队的研究成果以“Superconductivity in pressurized trilayer La4Ni3O10-δ single crystals”为题发表于最新一期的《自然》（Nature）。

Screenshot of research results All photos in this article are courtesy of Fudan University

Prof. Jun Zhao's team successfully grew a high-quality single crystal sample of three-layer nickel oxide La4Ni3O10 using high-pressure optical floating-zone technology, which confirmed the pressure-induced bulk superconductivity in nickel oxide, and its superconducting volume fraction reached 86%, which means that another new type of high-temperature superconductor has been discovered. The study also found that these materials exhibit exotic metals and unique interlayer coupling behaviors, which provides a new perspective and platform for understanding the mechanism of high-temperature superconductivity.

Zhao Jun (front row, third from left) group photo of the members of the research group

Superconductors refer to materials with zero resistance and complete diamagnetism at a specific transition temperature, which can be widely used in power transmission and energy storage, medical imaging, maglev trains, quantum computing and other fields, and have important scientific research and technical application value. Over the years, scientists around the world have carried out various forms of in-depth research on the phenomenon of high-temperature superconductivity, but after nearly 40 years of efforts, its formation mechanism is still an unsolved mystery.

An important topic in the study of high-temperature superconductivity is to find new high-temperature superconductors. On the one hand, it is hoped that clues to understand the mechanism of high-temperature superconductivity will be sought from new perspectives, and on the other hand, new material systems may also provide new application prospects.

In the research results released by Nature, Zhao Jun's team successfully synthesized a high-quality three-layer nickel oxide La4Ni3O10 single crystal sample, which exhibited zero resistance and complete diamagnetism at a temperature below the superconducting critical temperature, and the superconducting volume fraction reached 86%, which strongly demonstrated the bulk superconducting properties of nickel oxide.

"This superconducting volume fraction is close to that of copper oxide high-temperature superconductors, which undoubtedly confirms the bulk superconductivity of nickel oxides." Zhao Jun said.

Jun Zhao came to the Department of Physics at Fudan University in 2012 after his postdoctoral work at the University of California, Berkeley, focusing on neutron scattering of associated electronic systems such as high-temperature superconductivity and quantum magnetic materials, as well as the growth of large-scale, high-quality single-crystal samples and the measurement of their thermodynamic and transport properties.

"Most of the breakthroughs in high-temperature superconductivity research have been driven by experiments, especially the discovery of new superconductors, and there are still many phenomena that cannot be fully explained by existing theories." Zhao Jun introduced, "The growth conditions of nickel oxide single crystal samples are very harsh, and it is necessary to maintain high temperature and sharp temperature gradient in a specific high oxygen pressure environment to achieve stable growth of single crystal samples. Due to the small oxygen pressure window of phase formation, it is prone to the phenomenon of layered symbiosis of nickel oxides of multiple components, and a large number of defects of vertex oxygen positions are easy to occur during the growth process, which may be the reason for the low superconductivity content of nickel oxides. ”

The team used high-pressure optical float technology to grow a large number of samples, constantly searched for and summarized the rules, and after many failures, finally successfully synthesized a pure phase three-layer La4Ni3O10 nickel oxide single crystal sample. Furthermore, the team carried out a series of neutron diffraction and X-ray diffraction measurements to accurately determine the lattice structure and oxygen atomic coordinates and content of the material, and found that there were almost no vertex oxygen defects in it.

Based on high-quality single crystal samples, the team and collaborators used diamond-to-anvil technology to discover the pressure-induced superconducting zero resistance phenomenon of La4Ni3O10, and the superconducting critical temperature reached 30 K at 69 GPa. Based on diamagnetic data, the superconducting volume fraction of the single crystal sample is as high as 86%, confirming the bulk superconducting properties of nickel oxides.

The results of this study also delicately characterize the superconducting phase diagram of the La4Ni3O10 system under pressure, and clarify the relationship between charge density wave/spin density wave, superconductivity, exotic metal behavior, and crystal structure phase transition in the phase diagram. The results suggest that nickel oxide superconductivity may have different interlayer coupling mechanisms from copper oxide superconductivity, which provides important insights into the study of the mechanism of nickel oxide superconductivity, and provides an important material platform for exploring the complex interaction between spin sequence-charge order, flat band structure, interlayer correlation, exotic metal behavior and high-temperature superconductivity.

In the next step, Zhao Jun's team will continue to focus on major issues in the field of high-temperature superconductivity, explore the internal relationship and mechanism of high-temperature superconductors in different systems, and understand and discover higher-performance high-temperature superconductors.

Zhao Jun, a professor at Fudan University, Guo Jiangang, a researcher at the Institute of Physics of the Chinese Academy of Sciences, and Zeng Qiaoshi, a researcher at the Beijing High Voltage Research Center, are the co-corresponding authors of the paper. Zhu Yinghao, a postdoctoral fellow in the Department of Physics of Fudan University, Peng Di, a doctoral student at the Beijing High Voltage Science Research Center, Zhang Enkang from the Department of Physics of Fudan University, Pan Bingying, an associate professor at Ocean University of China, and Chen Xu, an engineer from the Institute of Physics of the Chinese Academy of Sciences, are the co-first authors.

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