Between science and media hype - Searching for room-temperature superconductors
Superconductors at room temperature and atmospheric pressure could fundamentally change our modern world: low-cooling data centers, efficient power grids, advances in nuclear fusion. What sounds like the fulfillment of a dream unfortunately has a few catches.
Update September 2023:
At the EUCAS (European Conference on Applied Superconductivity), the current state of research on room-temperature superconductors was explained in an easy-to-follow panel discussion. One of the scientists who participated in the discussion was Professor Tabea Arndt from ITEP. The recording of the event (55 min) is available here, it's definitely worth a look!
On July 22, 2023, a Korean research group led by Sukbae Lee published a pre-print paper claiming to have found the world's first superconductor at room temperature and normal pressure – a lead apatite modified with copper, named LK-99 by the authors. Social media was abuzz, but the physic researchers remained skeptical. The results were rushed and incompletely documented. And after a few weeks of wild speculation and heated debates, no independent research group has yet managed to reliably reproduce the experiment's results.
Great claims, scarce evidence
Experts in superconductors at ITEP also reacted cautiously to the news from Korea. Professor Bernhard Holzapfel summarizes the problem: "Physically, there is nothing to prevent such a room-temperature superconductor from existing. However, reports have been appearing regularly for years proclaiming the great breakthrough. None of them has been verified to date." Among experts, such unconfirmed superconductor materials are jokingly referred to as USOs (Unidentified Superconducting Objects), as for example most recently in March 2023.
A rigorous selection process
Prof. Holzapfel emphasizes that a particularly good data set is needed to go public with a finding like this. "As is well known, extraordinary claims require extraordinary evidence. In any case, I would measure ten times before publishing results with this kind of societal impact." For example, it is not sufficient evidence for superconductivity that a material levitates above a magnet, because other diamagnetic materials such as graphite can do that as well. Even water is slightly diamagnetic, so that it is possible to levitate frogs above high-field magnets.
Superconductors must be ideal diamagnets up to a certain magnetic field strength, i.e. they must completely displace a magnetic field from their interior. In addition, loss-free current transport must also be experimentally proven: In true superconductors, the electrical resistance suddenly drops to zero upon being cooled. Corresponding experiments must have high measurement accuracy.
The long journey to practical applications
But what would be the next steps if researchers were to actually discover a room-temperature superconductor? First of all, it would have to be extensively tested for up to which critical current and magnetic field strengths the material exhibits superconductivity in the first place – after all, these variables, which are extremely relevant to applications, vary greatly depending on the superconductor. But even if the material under investigation has optimal properties in all of these areas, new manufacturing processes will probably have to be developed for the cost-effective production of corresponding cables or wires. That could take several years. So the idea that such a "super material" will be discovered today and used in a game console tomorrow is unfortunately somewhat naïve.
However, this does not mean that superconductor research is pointless. For example, the established copper oxide-based superconductors that superconduct at liquid nitrogen (-196°C) show excellent properties for energy and magnet applications. The first products based on them are already on the market or in development, despite cooling necessities. Scientists at ITEP and around the world are regularly making major advances that contribute to a deeper physical understanding of superconductivity and its applications. New superconducting applications with revolutionary properties, such as extremely compact motors or cables, will come on the market in the next few years, and perhaps one day a room-temperature superconductor under normal pressure will indeed be one of them – we remain cautiously optimistic.