Home Science Room-temperature superconductor ‘breakthrough’ met with scepticism

Room-temperature superconductor ‘breakthrough’ met with scepticism

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Room-temperature superconductor ‘breakthrough’ met with scepticism

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LK-99 partially levitating

LK-99 partially levitating

Hyun-Tak Kim et al. (2023)

A team of researchers claims to have created the first materials that conduct electricity perfectly at room temperature and ambient pressure, but many physicists are highly sceptical. Speaking to New Scientist, Hyun-Tak Kim at the College of William & Mary in Virginia says he will support anyone trying to replicate his team’s work.

Superconductors are materials through which electricity can move without encountering any resistance, and so would significantly cut down the energy costs of electronics. But for over a century, researchers have been unable to make them work except under extreme conditions like very low temperatures and remarkably high pressures.

Now, Kim and his colleagues claim to have made a material that is superconductive at room temperature and pressure.

If their claims hold up to scientific scrutiny, this new work would be truly extraordinary, so the burden of proof for the research team is equally exceptional. The fact that some previous reports of breakthroughs in superconductivity were later retracted and that other teams failed to replicate the results also raises the stakes.

To make the new material, called LK-99, Kim and his colleagues mixed several powdered compounds containing lead, oxygen, sulphur and phosphorus, then heated them at a high temperature for several hours. This made the powders chemically react and transform into a dark grey solid.

The researchers then measured how much a millimetre-sized sample of LK-99 resisted electricity passing through it at different temperatures and found that its so-called resistivity fell sharply from a sizeable positive value at 105°C (221°F) down to nearly zero at 30°C (86°F).

The researchers also tested the material’s response to a magnetic field at a range of temperatures because superconductors are known to expel them as part of a phenomenon called the Meissner effect. They concluded that it did exhibit this effect in the temperature range where it also had near zero resistance.

Because of the Meissner effect, a superconductor floats when placed on a conventional magnet and the researchers recorded a test of this levitation as well. In their video, they placed a piece of LK-99 above a magnet and it clearly rises above the magnet’s surface.

However, only one edge of the flat, coin-like material fully levitates, while the other seems to stay in contact with the magnet. Kim says this is due to the sample being imperfect, which means that only some part of it becomes superconductive and exhibits the Meissner effect.

Currently, two papers concerning LK-99 are available on the preprint service arXiv, which does not conduct peer review, and a related past study was published in the Journal of the Korean Crystal Growth and Crystal Technology in April. Kim has only co-authored one of the arXiv papers, while the other is authored by his colleagues at the Quantum Energy Research Centre in South Korea, some of whom also applied for a patent on LK-99 in August 2022.

Both papers present similar measurements, however Kim says that the second paper contains “many defects” and was uploaded to arXiv without his permission. In that paper, the work is described as opening a “new era for humankind”.

Some commentators on social media heralded the findings as a generational breakthrough, but the overwhelming response from researchers with expertise in superconductivity has been largely sceptical.

Susannah Speller and Chris Grovenor at the University of Oxford say that when a material becomes superconductive, there should be clear signatures of that in a number of measurements.

For two of those in particular, namely the response to a magnetic field and a quantity called heat capacity, Speller says neither is demonstrated in the data. “So it is too early to say that we have been presented with compelling evidence for superconductivity in these samples,” she says.

Other experts that New Scientist consulted were similarly sceptical about the results and the data produced. Some raised concern that some of the results could be explained by errors in experimental procedure combined with imperfections in the LK-99 sample.

The theoretical models that Kim and his colleagues cite as explaining why the new material can superconduct at such different conditions than all previous ones have also been called into question by one of the researchers that New Scientist spoke to.

Kim says that he is aware of the scepticism but believes that other researchers should try to replicate his team’s work to settle the issue. Once the findings are published in a peer-reviewed journal, which Kim says is in the works, he will support anyone who wants to create and test LK-99 for themselves. In the meantime, he and his colleagues will continue to work on perfecting their samples of the alleged miracle superconductor and move towards mass-producing it.

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