Researchers from the Texas Center for Superconductivity (TcSUH) and the department of physics at the University of Houston have broken the temperature record for superconductivity at ambient pressure — a breakthrough that could eventually lead to more efficient ways to generate, transmit and store energy.
The UH team achieved a transition temperature (Tc) of 151 Kelvin (about minus 122 degrees Celsius) under ambient pressure — the highest ever recorded for all the reported superconductors at ambient pressure since the discovery of superconductivity in 1911. The transition temperature is the point below which a material becomes superconducting, meaning electricity can flow through it without resistance.
Raising this temperature has been a major goal in superconductivity research for decades. The closer scientists can push the Tc toward room temperature, the more practical and affordable superconducting technologies could become.
The research by UH physicists Ching-Wu Chu and Liangzi Deng was published March 9 in the Proceedings of the National Academy of Sciences. The work was funded by Intellectual Ventures , a global invention and investment company, the state of Texas via TcSUH and other foundations.
“Transmitting electricity in the grid loses about 8% of the electricity,” said Chu, professor of physics, TcSUH founding director and the paper’s senior author. “If we conserve that energy, that’s billions of dollars of savings and it also saves us lots of effort and reduces environmental impacts.”
Superconductors allow electricity to flow without resistance, which makes them useful for improving electrical grids, building advanced medical imaging systems, enabling fusion energy technologies and developing faster electronics. However, most superconductors must be cooled to extremely low temperatures, which makes them expensive and difficult to use.
“Once we bring the material to ambient pressure, it becomes much more accessible for scientists to use well-developed instrumentation to investigate it and further develop technologies for ambient condition operations,” said Deng, assistant professor of physics, principal investigator at the TcSUH and lead author of the paper.
Breaking the Temperature Barrier
For more than a half century, scientists made steady progress in their search for new kinds of superconducting materials with higher Tc. A groundbreaking 1987 discovery by Chu and colleagues found a material called YBCO reaches superconductivity at minus 180 degrees C, or 93 K, ushering in the worldwide race to develop high-temperature superconductors.
Subsequently, a mercury-based, copper-oxide ceramic, known as Hg1223, that superconducts at up to minus 140 degrees C, or 133 K, was discovered in 1993 and held the ambient pressure record Tc until now.
The UH team increased it by 18 degrees C to reach 151 K.
This advance was made possible through a technique known as pressure quenching — a new approach for superconductors, though commonly used in other areas such as creating diamonds. In this method, researchers first apply intense pressure to the material to enhance its superconducting properties and raise its transition temperature.
While the material is under pressure, it is cooled to a specific temperature and rapidly released from pressure completely, effectively “locking in” the enhanced superconducting properties. Using this method, the researchers were able to preserve the higher Tc even after the pressure was removed, allowing the material to remain stable under normal conditions.
“Other researchers have shown that reaching superconductivity at room temperature under pressure is achievable,” Chu said. “Our method shows that it is possible to retain that state without maintaining pressure.”
Pushing the Research Forward
Although ambient-pressure room-temperature superconductivity — around 300 K — remains the ultimate goal, researchers said the new record represents an important step forward and is significant in the world of superconductivity.
“This finding has great potential,” Chu said. “We believe, with enough people working on it and given enough time, we should be able to realize the potential.”
Chu and Deng are also co-authors on a companion perspective paper from the study’s main funder, Intellectual Ventures. The complementary paper, also published in PNAS , outlines six different methods for tuning or transforming materials to reach higher-temperature superconductivity, one being pressure quenching, said Rohit Prasankumar, director of superconductivity research at Intellectual Ventures.
“Room-temperature superconductivity has been seen as a ‘holy grail’ by scientists for over a century,” Prasankumar said. “The UH team’s result shows that this goal is closer than ever before. However, the distance between the new record set in this study and room temperature is still about 140 degrees C. Closing this gap will require concerted, intentional efforts by the broader scientific community, including materials scientists, chemists, and engineers, as well as physicists.”
Proceedings of the National Academy of Sciences