Superconductors Take a Leap Toward Room Temperature

Superconductors have been kept in a sort of scientific cold storage for over a century. The first one, a wire made of solid mercury, was found in 1911 in a quiet Dutch laboratory where Heike Kamerlingh Onnes had been covering objects with liquid helium to observe the effects. At four degrees above absolute zero, the material’s electrical resistance simply disappeared. That marked the beginning of one of the longest and most bizarre hunts in physics. Since then, the dream has hardly changed: discover a substance that performs the same function at a kitchen counter’s temperature.

That search has been accelerated by a recent theoretical paper from Queen Mary University of London that was accepted in the Journal of Physics: Condensed Matter earlier this year. The group, which includes Chris Pickard of Cambridge and Kostya Trachenko, contends that the upper limit for superconducting temperature is not some arbitrary engineering wall. It is related to the Planck constant, electron mass, and electron charge—the deepest constants of nature. That ceiling falls between a few hundred and a thousand Kelvin when you do the math. Almost casually, room temperature falls within that range.

That has a subtle thrill to it. It implies that what scientists have been pursuing is not being actively blocked by the universe. Pickard told the journal in simple terms, “The dream is still alive,” which is unusual for a physicist. The implication is that our materials, techniques, and patience—rather than the laws of physics themselves—are the barrier.

By raising critical temperatures to the point where liquid nitrogen could be used in place of helium, the cuprates of the 1980s altered the discourse, winning a Nobel Prize and starting a whole industry. There was a protracted, annoying plateau after that. In the 2010s, hydrogen-rich compounds started to break records by reaching superconductivity at temperatures close to freezing, but only when compressed between diamonds at pressures similar to those found in the Earth’s core. It’s useless for a power line that crosses Nebraska, but useful for a lab bench.

Then, in the summer of 2023, the dark, copper-laced lump of South Korean apatite known as LK-99 briefly took over social media. Every corner of the internet that dealt with physics for roughly three weeks was filled with grainy videos of tiny pieces of mineral wobbling over magnets. Since then, the majority of those assertions have been shown to be false. However, the response itself, the sense of desperation in the air, and the way scientists worldwide abandoned their efforts to test it were telling. People desired for it to be authentic.

A more sober kind of progress was made last year. Within an antiferromagnetic insulator, a team at SLAC and Stanford discovered electron pairing, the fundamental process that drives superconductors, occurring at higher temperatures than anticipated. There were the pairs. They just weren’t in sync. According to Ke-Jun Xu, a graduate student at Stanford, the electrons “are telling us that they are ready to be superconducting, but something is stopping them.” Such a discovery implies that the puzzle is now mechanical rather than metaphysical.

It’s difficult to ignore how these headlines have changed in texture. Room-temperature superconductivity was practically a joke ten years ago. AI-powered search engines, materials chemists, and theorists are all coming together in one area these days. Something seems to be coming loose. It’s unclear if this will result in a material that can be used in five or fifty years, but at last, the field seems to be progressing rather than waiting.