MATHEMATICAL SCIENCES

Scientists discovered the first nickel oxide high-temperature superconductor in the liquid nitrogen temperature zone


On July 12, Nature published online the latest research results of Professor Wang Meng’s team and collaborators at the School of Physics of Sun Yat-sen University: the discovery of the first nickel oxide high-temperature superconductor in the liquid nitrogen temperature zone. According to reports, the material has become the second type of oxide high-temperature superconductor to enter the liquid nitrogen temperature zone after the copper oxide high-temperature superconductor discovered in 1986.

“Superconductivity in the liquid nitrogen temperature zone was found in a completely new system, which exceeded our expectations.” Wang Meng, co-corresponding author of the paper and professor at the School of Physics at Sun Yat-sen University, told China Science News that the team synthesized a nickel oxide single crystal and found superconductivity of 80K (minus 193 degrees Celsius) at 14GPa pressure for the first time.

Professor Wang Meng of the School of Physics of Sun Yat-sen University demonstrated nickel oxide La3Ni2O7 single crystal. Photo by Li Jianping

Nature reviewers spoke highly of the work, saying it was “of outstanding importance,” “groundbreaking discovery,” and “widely watched by the industry.”

A major breakthrough from 0 to 1

More than 100 years ago, scientists discovered that mercury has zero electrical resistance at certain low temperatures, a phenomenon known as “super conductivity.” Due to the remarkable characteristics of zero resistance and antimagnetism, superconductors have broad application prospects in many fields such as information technology, biomedicine, and scientific instruments, but now superconductors can only occur superconductivity at low temperatures, and their large-scale application is seriously limited.

In 1986, Dutch scientists discovered copper oxide superconductors, and the superconducting transition temperature exceeds the liquid nitrogen temperature by 77K (minus 196 degrees Celsius). In 2008, Japanese scientists discovered superconductivity in an iron arsenic-based material. Soon, Chinese scientists synthesized a variety of iron arsenic materials, raised the superconducting temperature of the block to a maximum of 55K, and promoted its application, but failed to enter the liquid nitrogen temperature zone.

Superconducting materials have the special properties of absolute zero resistance, complete diamagnetism and macroscopic quantum tunneling effect, so they have important scientific and application value. After nearly 40 years of research, copper oxide is still the only unconventional superconductor that enters the liquid nitrogen temperature zone, and its superconducting mechanism is still unknown, and scientists around the world have been committed to finding unconventional superconducting materials and solving the high-temperature superconducting mechanism.

“Scientists have mastered many experimental phenomena and laws in the study of copper oxide superconductivity, but the causal relationship with high-temperature superconductivity cannot be determined.” Zhang Guangming, co-corresponding author of the paper and professor at Tsinghua University, pointed out that the mechanism of high-temperature superconductivity is still unknown and has become one of the most important scientific problems in physics in the past 40 years.

“No one knows where the end point is, and if we do, we can design a path to the end, but basic research is to unlock the unknown, and the unknown is full of uncertainty.” Wang Meng said that no one can predict that new materials will definitely bring new breakthroughs.

Fortunately, this time, Wang Meng’s team succeeded. Their discovery of superconducting nickel oxides in the liquid nitrogen temperature region for the first time means that they have opened up a new field for world superconductivity research and will lead the direction of superconductivity research.

The reporter learned that the discovery is a breakthrough in the field of basic research “from 0 to 1”, which is expected to promote the cracking of the high-temperature superconducting mechanism, make it possible to design and predict high-temperature superconducting materials, and achieve a wider and larger industrial application.

Three years to sharpen a sword

In the laboratory of the School of Physics of Zhesheng Tang on the South Campus of Sun Yat-sen University’s Guangzhou campus, Wang Meng’s team showed us a black rod of several centimeters. This is exactly the “new star” discovered this time – a single crystal sample of La3Ni2O7, a new high-temperature superconducting material. This seemingly “unpretentious” rod condenses the team’s years of hard work.

Over the past three years, Wang Meng’s team has synthesized high-quality single crystal samples of nickel oxide (La3Ni2O7) system through continuous exploration of conditions, and has taken the lead in systematic research in the world. “After synthesizing the nickel oxide single crystal sample, we demonstrated that it exhibits a high-temperature superconductivity of 80K at pressures in excess of 14 gigapascals.”

“The growth conditions of La3Ni2O7 are extremely harsh, the average valence state is 2.5 valence, the stable valence state of Ni is positive 2 valence, and the oxygen pressure range is narrow, and it took the research team more than two years to explore the growth conditions and grow high-quality single crystal samples.” Wang Meng introduced.

Huo Mengwu, a doctoral student at the School of Physics of Sun Yat-sen University, introduced the development of the team. Photo by Zhu Jiahao

Huo Mengwu, co-first author of the paper and a doctoral student at the School of Physics of Sun Yat-sen University, said that high-voltage research technology is complex and the research cycle is long. The research team spent more than a year systematically studying different nickel oxide material systems, and finally found a high-temperature superconductivity of 80K under pressure in La3Ni2O7 single crystals.

According to Huo Mengwu, the nickel oxide discovered this time is the second unconventional superconducting system known to mankind to reach the liquid nitrogen temperature zone, and scientists can conduct superconducting mechanism and application research in new material systems.

“Liquid nitrogen is cheaper to prepare than mineral water, and exceeding the liquid nitrogen temperature also means that superconducting materials require a low-temperature environment that is more readily available, and therefore has greater application potential.” Wang Meng said that the commonality of copper oxide and nickel oxide high-temperature superconductors will be studied next, and the solution of high-temperature superconductivity mechanism will be further promoted.

It is expected to crack the mechanism of high-temperature superconductivity

Wang Meng’s team carried out experimental research on La3Ni2O7 single crystal materials on the high-voltage experimental research platform of Sun Yat-sen University, South China University of Technology, Institute of Physics of the Chinese Academy of Sciences, and Beijing synchrotron radiation device, and quickly determined that it was transformed into a superconductor under pressure, and the superconducting transition temperature reached the liquid nitrogen temperature range, up to 80K.

“This time the discovery of high-temperature superconducting nickel oxide, nickel valence state of +2.5 valence, beyond traditional expectations, its electronic structure, magnetism and copper oxide are completely different. Through comparative studies, it will be possible to identify the key factors of high-temperature superconductivity and push scientists to decipher the mechanism of high-temperature superconductivity. Wang Meng introduced, “According to the mechanism, it is expected that after intersecting with computers, AI technology and other disciplines, new and more easily applicable high-temperature superconducting materials will be designed and synthesized to achieve a wider range of applications.”

“Sun Yat-sen University has been building a public research platform for the School of Physics since 2017, which has created first-class conditions for the team’s material growth and characterization experiments.” Wang Meng said that the neutron spectrometer built by Sun Yat-sen University will also help the team to further study materials and promote the solution of the mechanism.

Professor Wang Meng of the School of Physics of Sun Yat-sen University instructs students. Photo by Wu Junhao

“At present, our superconducting materials require 14GPa pressure to achieve, which will limit the study and wide application of superconducting mechanisms. The research team is currently working on the key problem, hoping to grow nickel oxide superconductors that reach superconductivity in the liquid nitrogen temperature zone at atmospheric pressure. Wang Meng said.

Zhang Guangming said that nickel-based oxide superconductors have a crystal structure and electronic structure different from copper-oxygen high-temperature superconductors, and the new findings have brought many important enlightenments to our understanding of the mechanism of high-temperature superconductivity, which will help to crack the microscopic mechanism of high-temperature superconductivity, make it possible to design and predict high-temperature superconducting materials, and realize the wide application of superconducting materials in the liquid nitrogen temperature zone.

At present, Wang Meng’s team has received applications from scientists from all over the world for sample cooperative research, and it is foreseeable that nickel oxide high-temperature superconductivity research will usher in a new wave of enthusiasm. (Source: China Science News, Zhu Hanbin, Li Jianping)

Related paper information:https://doi.org/10.1038/s41586-023-06408-7



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