For nearly three decades, the mercury-based superconductor Hg1223 held the record for the highest transition temperature achievable at normal atmospheric pressure. This month, that record finally fell.
Researchers at the University of Houston's Texas Center for Superconductivity announced they have achieved superconductivity at 151 Kelvin (about minus 122 degrees Celsius) under ambient pressure, surpassing the previous record of 133 Kelvin by 18 degrees. The research, published in the Proceedings of the National Academy of Sciences, represents the highest transition temperature recorded for any superconductor at normal pressure since the phenomenon was first discovered in 1911.
The breakthrough came through a technique called pressure-quenching. Physicists Paul Ching-Wu Chu and Liangzi Deng applied intense pressure to the material to enhance its superconducting properties, then rapidly released the pressure while the sample was cooled to a specific temperature. This process effectively freezes the improved properties into place, allowing the material to remain stable at ambient pressure without losing its superconducting behaviour.
The significance of this shift should not be understated. Before this breakthrough, materials that exhibited the highest superconducting temperatures could only be studied under extreme pressure using diamond anvil cells, which severely limited investigation. The new technique opens up practical pathways for scientists to use standard laboratory instrumentation to analyse and refine superconducting materials.
However, the finish line remains far more distant than the distance already travelled. Room temperature sits around 293 Kelvin, or 20 degrees Celsius. The 151 Kelvin achievement leaves researchers approximately 140 degrees Celsius short of the ultimate goal. In practical terms, scientists would need to push transition temperatures upward by a factor equivalent to nearly nine times the improvement just achieved, and do it repeatedly, to reach room-temperature superconductivity.
Rohit Prasankumar, director of superconductivity research at Intellectual Ventures, which funded the work, acknowledged both the progress and the scale of the challenge remaining. "Room-temperature superconductivity has been seen as a 'holy grail' by scientists for over a century. The UH team's result shows that this goal is closer than ever before. However, closing this gap will require concerted, intentional efforts by the broader scientific community, including materials scientists, chemists, and engineers, as well as physicists."
The potential applications of even the current advance are substantial. Superconductors allow electricity to flow without resistance, which could dramatically improve the efficiency of electrical grids, medical imaging systems, and fusion energy technologies. Today, about eight percent of energy is lost during transmission across power networks. Superconductors operating at more accessible temperatures could eliminate such losses, though substantial cooling requirements mean practical deployment remains costly and complex.
The field has weathered significant setbacks in recent years. High-profile claims of room-temperature superconductivity, most notably from researcher Ranga Dias, were subsequently retracted or disputed. These episodes highlight how challenging reliable progress can be in this field, where theoretical understanding remains incomplete and competing claims often fail replication attempts.
The Houston team's approach differs because it builds incrementally on established physics. Pressure-quenching itself is not new; diamond manufacturers have used similar processes for decades. The innovation lies in demonstrating that this well-understood technique can stabilise superconducting states at ambient pressure, creating a reproducible pathway rather than chasing exotic claims.
The work also serves as a reminder that scientific progress is often measured not by dramatic leaps but by persistent advancement. Thirty years without improvement might suggest stagnation. The new record suggests renewed momentum, though everyone in the field recognises that the hardest work likely lies ahead.