Many Physicists 'Skeptical' of Spectacular Superconductor Claims

"This week, social media has been aflutter over a claim for a new superconductor that works not only well above room temperatures, but also at ambient pressure," writes Science magazine.If true, the discovery would be one of the biggest ever in condensed matter physics and could usher in all sorts of technological marvels, such as levitating vehicles and perfectly efficient electrical grids. However, the two related papers, posted to the arXiv preprint server by Sukbae Lee and Ji-Hoon Kim of South Korea's Quantum Energy Research Centre and colleagues on 22 July, are short on detail and have left many physicists skeptical... "They come off as real amateurs," says Michael Norman, a theorist at Argonne National Laboratory. "They don't know much about superconductivity and the way they've presented some of the data is fishy." On the other hand, he says, researchers at Argonne and elsewhere are already trying to replicate the experiment. "People here are taking it seriously and trying to grow this stuff." Nadya Mason, a condensed matter physicist at the University of Illinois, Urbana-Champaign says, "I appreciate that the authors took appropriate data and were clear about their fabrication techniques." Still, she cautions, "The data seems a bit sloppy...." What are the reasons for skepticism? There are several, Norman says. First, the undoped material, lead apatite, isn't a metal but rather a nonconducting mineral. And that's an unpromising starting point for making a superconductor. What's more, lead and copper atoms have similar electronic structures, so substituting copper atoms for some of the lead atoms shouldn't greatly affect the electrical properties of the material, Norman says. "You have a rock, and you should still end up with a rock." On top of that, lead atoms are very heavy, which should suppress the vibrations and make it harder for electrons to pair, Norman explains. The papers don't provide a solid explanation of the physics at play. But the researchers speculate that within their material, the doping slightly distorts long, naturally occurring chains of lead atoms... [Mason] notes that Lee and Kim also suggest that a kind of undulation of charge might exist in the chains and that similar charge patterns have been seen in high-temperature superconductors. "Maybe this material really just hits the sweet spot of a strongly interacting unconventional superconductor," she says. The big question will be whether anybody can reproduce the observations...

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