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New room-temperature superconductor offers tantalising possibilities

Written by Kenneth Chang Scientists announced this week a tantalising advance toward the dream of a material that could effortlessly convey electricity in everyday conditions. Such a breakthrough could transform almost any technology that uses electric energy, opening new possibilities for your phone, magnetically levitating trains and future fusion power plants. Usually, the flow of electricity encounters resistance as it moves through wires, almost like a form of friction, and some energy is lost as heat. A century ago, physicists discovered materials, now called superconductors, where the electrical resistance seemingly magically disappeared. But these materials only lost their resistance at unearthly, ultracold temperatures, which limited practical applications. For decades, scientists have sought superconductors that work at room temperatures. This weeks announcement is the latest attempt in that effort, but it comes from a team that faces wide scepticism because a 2020 paper that described a promising but less practical superconducting material was retracted after other scientists questioned some of the data. The new superconductor consists of lutetium, a rare earth metal, and hydrogen with a little bit of nitrogen mixed in. It needs to be compressed to a pressure of 145,000 pounds per square inch before it gains its superconducting prowess. That is about 10 times the pressure that is exerted at the bottom of the oceans deepest trenches. But it is also less than one one-hundredth of what the 2020 result required, which was akin to the crushing forces found several thousand miles deep within the Earth. That suggests that further investigations of the material could lead to a superconductor that works at ambient room temperatures and at the usual atmospheric pressure of 14.7 pounds per square inch. This is the start of the new type of material that is useful for practical applications, Ranga P Dias, a professor of mechanical engineering and physics at the University of Rochester in New York, said to a room packed full of scientists on Tuesday at a meeting of the American Physical Society in Las Vegas. A fuller accounting of his teams findings was published Wednesday in Nature, the same journal that published, then retracted the 2020 findings. The team at Rochester started with a small, thin foil of lutetium, a silvery white metal that is among the rarest of rare earth elements, and pressed it between two interlocking diamonds. A gas of 99% hydrogen and 1% nitrogen was then pumped into the tiny chamber and squeezed to high pressures. The sample was heated overnight at 150 degrees Fahrenheit, and after 24 hours, the pressure was released. About one-third of the time, the process produced the desired result: a small vibrant blue crystal. Doping nitrogen into lutetium hydride is not that easy, Dias said. In one of the University of Rochester laboratory rooms used by Dias group, Hiranya Pasan, a graduate student, demonstrated the surprising hue-changing property of the material during a reporters visit last week. As screws tightened to ratchet up the pressure, the blue turned into a blushing tint. It is very pink, Dias said. With even higher pressures, he said, it goes to a bright red. Shining a laser through the crystals revealed how they vibrate and unlocked information about the structure. In another room, other members of Dias team were making magnetic measurements on other crystals. As the temperatures dropped, the expected squiggles appeared in the data plotted on a computer screen, indicating a transition to a superconductor. This is a live measurement were doing right now, Dias said. In the paper, the researchers reported that the pink crystals exhibited key properties of superconductors, like zero resistance, at temperatures up to 70 degrees Fahrenheit. Im cautiously optimistic, said Timothy Strobel, a scientist at the Carnegie Institution for Science in Washington who was not involved in Dias study. The data in the paper, it looks great. If this is real, its a really important breakthrough, said Paul C W Chu, a professor of physics at the University of Houston who also was not involved with the research. However, the if part of that sentiment swirls around Dias, who has been dogged by doubts and criticism, and even accusations by a few scientists that he has fabricated some of his data. The results of the 2020 Nature paper have yet to be reproduced by other research groups, and critics say that Dias has been slow to let others examine his data or perform independent analyses of his superconductors. The editors of Nature retracted the earlier paper last year over the objections of Dias and the other authors. Ive lost some trust in whats coming from that group, said James Hamlin, a professor of physics at the University of Florida. Nonetheless, the new paper made it through the peer review process at the same journal. Having a paper retracted does not automatically disqualify an author from submitting new manuscripts, a spokesperson for Nature said. All submitted manuscripts are considered independently on the basis of the quality and timeliness of their science. At the conference on Tuesday in Las Vegas, so many physicists crowded a narrow meeting room that a moderator asked some to leave so that they wouldnt have to cancel the presentation. Once the room thinned out, Dias was able to present his findings with no interruptions. As he thanked the crowd, the moderator expressed regret that they had run out of time for questions. Strobel acknowledged the continuing controversy around Dias and the earlier extraordinary claims that have yet to be reproduced. I dont want to read into it too much, but there could be a pattern of behaviour here, Strobel said. He really could be the best high-pressure physicist in the world, poised to win the Nobel Prize. Or theres something else going on. Under pressure Superconductivity was discovered by Heike Kamerlingh Onnes, a Dutch physicist, and his team in 1911. Not only do superconductors carry electricity with essentially zero electrical resistance, but they also possess the strange ability known as the Meissner effect that ensures zero magnetic field inside the material. The first known superconductors required temperatures only a few degrees above absolute zero, or minus 459.67 degrees Fahrenheit. In the 1980s, physicists discovered so-called high-temperature superconductors, but even those became superconducting in conditions far more frigid than those encountered in everyday use. The standard theory explaining superconductivity predicts that hydrogen should be a superconductor at higher temperatures if it could be squeezed hard enough. But even the most resilient of diamonds break before reaching pressures of that magnitude. Scientists started looking at hydrogen mixed with one other element, surmising that the chemical bonds might help compress the hydrogen atoms. In 2015, Mikhail Eremets, a physicist at the Max Planck Instit

Thursday, March 9, 2023 at 3:01 am

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