Researchers from the Texas Center for Superconductivity (TcSUH) and the Department of Physics at the University of Houston set a new record for superconductivity at ambient pressure when they achieved a transition temperature (Tc) of 151 Kelvin (about –122°C) under ambient pressure. The Tc is the point below which a material becomes superconducting, meaning electricity can flow through it without resistance.

This is the highest recorded Tc since the discovery of superconductivity in 1911. Raising this temperature has been a major goal in superconductivity research for decades because the closer the Tc gets to room temperature, the more practical and affordable superconducting technologies could become, which could lead to more efficient ways to generate, transmit and store energy, as well as possibly improving the electrical grid.

Superconductors eliminate resistance, allowing electricity to flow more easily. But because they must be cooled to extremely low temperatures, superconductors are expensive and difficult to use.

Furthermore, UH physicist Ching-Wu Chu, TcSUH’s founding director and chief scientist and the paper’s senior author, explains that about 8% of electricity in the grid is lost during transmission due to resistance. Conserving that energy could save billions of dollars and reduce environmental impact.

The quest to develop high-temperature superconductors became competitive in 1987 after Chu and colleagues discovered that a material called YBCO reaches superconductivity at –180°C, or 93 K.

In 1993, a mercury-based, copper-oxide ceramic, known as Hg1223, that superconducts at up to –140°C, or 133 K, was discovered. The UH team increased it by 18°C to reach 151 K—a new record.

To achieve that, they used a technique known as pressure quenching. Commonly used to create diamonds, it was a new approach for superconductors. It involves applying intense pressure to the material to enhance its superconducting properties and raise its Tc. While under pressure, the material is cooled to a specific temperature and rapidly released from pressure completely. This “locks in” the enhanced superconducting properties, allowing the material to remain stable under normal conditions.

While reaching superconductivity at room temperature under pressure is achievable, Chu said their method shows that it is possible to retain that state without maintaining pressure. At ambient pressure, the material is more accessible for scientists to develop technologies for ambient condition operations, which could lead to achieving the ultimate goal of reaching ambient-pressure room-temperature superconductivity (around 300 K).

“Room-temperature superconductivity has been seen as a ‘holy grail’ by scientists for over a century,” said Rohit Prasankumar, director of deep science and enterprise science funds at Intellectual Ventures, Bellevue, Wash., which helped fund the research. “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°C.”