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Why Experts Are Skeptical About That Supposed Superconductor Breakthrough

8 minute read

On Saturday July 22, researchers in South Korea published a paper announcing the synthesis of what could be the world’s first ambient-temperature superconductor.

If their findings are genuine, then the implications are huge. But most experts are skeptical. Researchers around the world are trying to replicate and verify the Korean researchers’ findings. The most credible attempts have found that LK-99—the name the Korean researchers gave the material—is not actually superconductive at room temperatures. 

For now, the reliability of the findings remains unclear. Researchers stress that we should know soon whether the researchers truly made a breakthrough.

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What are superconductors?

A superconductor is a material that can levitate in a magnetic field and conduct electricity without resistance—when cables get hot, that’s because of resistance. There are a number of materials that exhibit superconductivity at temperatures ranging from 4 Kelvin, -452.5°F, for mercury to 250 Kelvin, -9.7°F, for lanthanum hydride under high pressures. The large magnetic fields required for MRI scanners, for example, are generated by passing a large current through a superconductor (typically MRI machines use niobium titanium superconductors cooled to below 9.3 Kelvin, -442.9°F, using liquid helium).

But the low temperatures required mean that superconductors can only be used in specialized settings. Scientists have long been searching for a material that exhibits ambient-temperature superconductivity—in other words, a material that wouldn’t need to be cooled in order to be useful.

Ambient-temperature superconductors could be used to create efficient electricity grids—currently around 5% of energy transmitted and distributed in the U.S. is lost due to resistance. Computer chips made with superconducting materials could be 50 to 100 times as efficient as today’s computer chips, which would help reduce the climate cost of data centers. Superfast trains could levitate on the superconducting material.

Reasons to be skeptical

In 2020, researchers from the University of Rochester led by Ranga Dias, an assistant professor in the university’s physics and mechanical engineering departments, claimed they had discovered a method for placing carbon, sulfur, and hydrogen between the tips of two diamonds and compressing them to extremely high pressure to produce a carbon-sulfur-hydrogen compound which exhibited superconductivity at 287 Kelvin (57°F). However, other researchers could not replicate their results and the paper was retracted.

There have been many similar cases before. “Going back, in the 1990s, there were sometimes reports of room temperature superconductivity, which later evaporated,” says Simon Clarke, a professor of chemistry at the University of Oxford.

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The unorthodox manner in which the Korean researchers published their findings has also led some to doubt whether the conclusions are reliable. Two separate non-peer reviewed papers were published to arXiv, a preprint server, on the same day. The first was submitted by Young-Wan Kwon, a professor at Korea University Graduate School of Converging Science and Technology, on Saturday 22 July, at 4:51 p.m. in Seoul. Young-Wan was one of three authors—also listed were Sukbae Lee and Ji-Hoon Kim, CEO and R&D director respectively at the Quantum Energy Research Centre in Korea. 

At 7:11 p.m. the same day, a second paper was submitted, this time by Hyun-Tak Kim, a researcher at the Electronics and Telecommunications Research Institute in Korea and a researcher professor of physics at the College of William & Mary in Virginia. Sukbae Lee and Ji-Hoon Kim, both of whom had been listed as authors in the first paper, were listed as authors in the second paper too. Three new authors were also listed: Sungyeon Im, SooMin An, and Keun Ho Auh, all of whom are researchers at the Quantum Energy Research Centre. Young-Wan Kwon was not listed on this paper. Hyun-Tak Kim told the New Scientist that the first paper contains “many defects” and was uploaded to arXiv without his permission.

The corresponding authors listed on both papers did not respond to TIME’s request for comment.

There are a number of issues with the quality of the papers, says Clarke. The Korean researchers did not synthesize a pure sample of LK-99, which is made by introducing a small amount of copper into a lead-phosphate mineral, and they didn’t carry out the types of analysis usually used to verify the structure of a newly discovered material. While they did report a measurement of no resistance, Clarke stressed measuring resistance reliably requires a pure sample, something that the Korean team did not produce.

The researchers also uploaded a video of a sample of LK-99 partially levitating. However, levitation could just mean that the material is diamagnetic—a common property found in many materials including copper—says Clarke. “A lot of things are diamagnetic…there are some experiments that have been done with very high magnetic fields where you can levitate a strawberry or a frog.”

Clarke, who used to be an editor at the Journal of Solid State Chemistry, was unimpressed by the papers. “If I'd received either of those, they wouldn't have met the quality threshold, even for [peer] review,” he says.

Taken together, the history of false alarms in this field, the issues with the quality of the new papers, and the unusual circumstances around their publishing means that most experts recommend skepticism until further evidence is obtained.

The race to replicate

Since the papers were published, a number of laboratories around the world have been trying to replicate the finding. So far, the most credible attempts have found that LK-99 is not superconductive.

On July 31, researchers from the National Physical Laboratory of India uploaded a paper to arXiv that found that LK-99 is not superconductive. V.P.S. (Veerpal Singh) Awana, chief scientist at the National Physical Laboratory, has been posting the details of his group's replication attempts on Facebook, including photos of the materials produced and details of his correspondence with Sukbae Lee, one of the Korean researchers. Awana told TIME how his team worked overtime to attempt to recreate the Korean team’s results as quickly as possible: “This weekend was quite hectic for us… My team was very busy.”

Also on July 31, researchers from Beihang University in Beijing uploaded a paper to arXiv that found that LK-99 is not superconductive. 

Meanwhile, researchers at Huazhong University of Science and Technology in China posted a video on Aug. 1, showing magnetic levitation of a LK-99 sample. The video is notable in that the sample appears to levitate at multiple different angles. This suggests it is a perfect diamagnet, a rarer property than simple diamagnetism, and one associated with superconductors. As of Aug. 3, the video has over 9 million views and is number one on the most trending list on Bilibili, a Chinese video-sharing website.

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Chang Haixin, a professor in the School of Materials Science and Engineering at Huazhong University told TIME that the video was uploaded by a postdoctoral researcher on his team. Chang stressed that the levitation observed does not necessarily mean that the material is a superconductor—there are many materials that exhibit strong diamagnetism, which could be hard to distinguish from perfect diamagnetism, that are not superconductors, such as bismuth and graphite. Chang’s research group was only able to synthesize the small amount of material seen in the video. They are in the process of synthesizing more, at a greater level of purity, in order to be able to perform other tests that are required to verify if a material is a superconductor.

The Korean Society of Superconductivity and Cryogenics has also established a verification committee. On Aug. 3, Yonhap News Agency reported that the Society has concluded that LK-99 is not a superconductor because it does not show the Meisnner effect—the name for when a superconducting material expels all external magnetic fields, causing it to levitate in the presence of a magnetic field. 

Researchers at Argonne National Laboratory in the U.S. are currently trying to replicate the findings, as are teams at the Center for Quantum Materials and Superconductivity at Sungkyunkwan University in Seoul, the Laboratory of Superconducting Materials and Applications at Korea University, and the Center for Novel States of Complex Materials Research at Seoul National University. 

Theorists have carried out calculations to explore what the properties of the compound the Korean researchers claim to have synthesized might be. While theoretical calculations can only suggest, not confirm, potential mechanisms of superconductivity, calculations made by the Lawrence Berkeley National Laboratory in California, Northwest University in Washinton, and Vienna University of Technology, as well as from University of Colorado Boulder National Renewable Energy Laboratory and King's College London, all found that LK-99 could be superconductive at room temperatures.

At the same time, a number of committed hobbyists and amateurs have also been trying to replicate the finding. Andrew McCalip, an engineer located in California who has access to the facilities required to synthesize materials like LK-99 through his employer, Varda Space Industries, has been posting his attempts to replicate the finding on X (formerly known as Twitter) and live streaming on Twitch, a video streaming platform. McCalip also commented on one of Awana’s Facebook posts, inviting him to “join us on Twitter.”

The general advice from experts is to wait. “My gut feeling is this: I am very hopeful this compound will be a superconductor,” said Awana, stressing patience. “In a week or so, we will be able to say.”

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Write to Will Henshall at will.henshall@time.com