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(This message was added in version 6.7.0.) in /home4/scienrds/scienceandnerds/wp-includes/functions.php on line 6114Source:https:\/\/www.quantamagazine.org\/room-temperature-superconductor-discovery-meets-with-resistance-20230308\/<\/a><\/br> In a packed talk on Tuesday afternoon at the American Physical Society\u2019s annual March meeting in Las Vegas, Ranga Dias<\/a>, a physicist at the University of Rochester, announced that he and his team had achieved a century-old dream of the field: a superconductor that works at room temperature and near-room pressure. Interest was so intense in the presentation that security personnel stopped entry to the overflowing room more than fifteen minutes before the talk. They could be overheard shooing curious onlookers away shortly before Dias began speaking.<\/p>\n The results, published today in Nature<\/em><\/a>, appear to show that a conventional conductor \u2014 a solid composed of hydrogen, nitrogen and the rare-earth metal lutetium \u2014 was transformed into a flawless material capable of conducting electricity with perfect efficiency.<\/p>\n While the announcement has been greeted with enthusiasm by some scientists, others are far more cautious, pointing to the research group\u2019s controversial history of alleged research malfeasance. (Dias strongly denies the accusations.) Reactions by 10 independent experts contacted by Quanta<\/em> ranged from unbridled excitement to outright dismissal, with many of the experts expressing some version of cautious optimism.<\/p>\n Previously, superconductivity has been observed only at frigid temperatures or crushing pressures \u2014 conditions that make those materials impractical for long-desired applications such as lossless power lines, levitating high-speed trains and affordable medical imaging devices. The newly forged compound conducts current with no resistance at 21 degrees Celsius (69.8 degrees Fahrenheit) and at a pressure of around 1 gigapascal. That\u2019s still a lot of pressure \u2014 roughly 10 times the pressure at the deepest point in the Marianas Trench \u2014 but it\u2019s more than 100 times less intense than the pressure required in previous experiments with similar materials.<\/p>\n \u201cIf it turns out to be correct, it\u2019s possibly the biggest breakthrough in the history of superconductivity,\u201d said James Hamlin<\/a>, a physicist at the University of Florida who was not involved in the work. If it\u2019s true, he said, \u201cit\u2019s an earth-shattering, groundbreaking, very exciting discovery.\u201d But incidents involving the team\u2019s previous work \u2014 including but not limited to a near-room-temperature superconductivity claim<\/a> published in Nature<\/em> in 2020 and retracted late last year \u2014 have cast a shadow across today\u2019s announcement. \u201cIt\u2019s hard to not wonder if some of the same problems that have gone unaddressed in previous work also exist in the new work,\u201d Hamlin said.<\/p>\n For more than a century, scientists have known that cooling most metals to temperatures within a few degrees of absolute zero brings about a dramatic metamorphosis. Around this \u201ccritical temperature,\u201d which varies from one material to another, electrons pair up and form a type of quantum fluid. Once this happens, electrons no longer bounce into atoms in the material \u2014 interactions that generate resistance \u2014 which allows them to flow with no energy loss.<\/p>\n The overarching goal of superconductivity research since then has been to raise the critical temperature.<\/p>\n For decades, physicists have made incremental progress, steadily raising the critical temperature by testing different combinations of elements. One promising class of materials, known as hydrides, emerged in recent years. Hydrides are compounds that combine the featherweight hydrogen with heavier atoms like sulfur or metals. The more hydrogen, the better for superconductivity, physicists believe. Researchers sometimes add in a dusting of other atoms, such as carbon or nitrogen, to further tweak its properties. The first superconducting hydride, reported in 2015<\/a>, hit its transition at around minus 70 degrees Celsius and 155 gigapascals of pressure (approaching half that of Earth\u2019s core). Within three years, the same group<\/a> and another<\/a> both whipped up even more hydrogen-rich \u201csuperhydride\u201d materials that could superconduct as high as minus 13 degrees Celsius and at 190 gigapascals.<\/p>\n The new study demolishes all past records. For the past few years, Dias\u2019 team has worked on a superhydride based on lutetium. To produce a sample, the team would bathe a thin film of lutetium in a perfume of 99% hydrogen and 1% nitrogen while baking it for a few days at 200 degrees Celsius. A diamond anvil cell would then compress the sample at 2 gigapascals of pressure. The team would then progressively loosen the anvil while testing the sample for superconducting properties. Dias said that out of hundreds of samples produced, they were able to observe superconductivity in dozens of samples even after the pressure was lowered to about 1 gigapascal.<\/p>\n To demonstrate superconductivity, the team hit three textbook benchmarks. At the critical temperature, they showed a drop in resistance and a peak in a property related to how readily a material warms up. The team also managed to directly measure the expulsion of a magnetic field from the samples \u2014 an unambiguous signature for superconductivity called the Meissner effect that has never before been convincingly demonstrated in a superhydride. Curiously, the sample also shifted in color from blue to pink to red in sync with its phase changes.<\/p>\n The paper\u2019s plots are exactly what researchers look for when they test for superconductivity. The strong evidence thrills many scientists who have spent decades searching for materials that can bring the phenomenon closer to everyday conditions.<\/p>\n \u201cI am really excited to see the result. And I don\u2019t in any way doubt that what they\u2019re observing is what it is,\u201d said Siddharth Saxena<\/a>, a physicist at the University of Cambridge who was not involved in the new work. Eva Zurek<\/a>, a theoretical chemist at the University at Buffalo who often communicates with the Rochester group but who was also not involved in the research, said that a material that superconducts under these conditions \u201cwould impact every aspect of our life in ways we cannot imagine.\u201d Hamlin agrees that the demonstration \u201cis a tour de force of every kind of measurement you would want to see on this material, producing exactly the type of data you would hope to see.\u201d<\/p>\n Yet Hamlin and other researchers insist that the group\u2019s past requires that today\u2019s historic claims be met with historic levels of scrutiny.<\/p>\n \u201cThere is a lot of evidence for superconductivity here if you take it at face value,\u201d said Jorge Hirsch, a physicist at the University of California, San Diego. \u201cBut I do not believe any of what these authors say. I am not sold at all.\u201d<\/p>\n Hirsch said his mistrust stems from a long history of allegations of research malfeasance made against previous and current members of the group, many of which he has pressed. Most recently, in 2020 Dias and his co-authors published a study of a carbonaceous sulfur hydride (CSH) that hit its critical transition at around 14 degrees Celsius (57.2 degrees Fahrenheit) and 267 gigapascals. Almost immediately, a handful of experts spotted unusual patterns in the data used to verify the material\u2019s response to magnetic fields. When Dias and his frequent collaborator, Ashkan Salamat<\/a>, a physicist at the University of Nevada, Las Vegas released their raw data a year later in the form of a 149-page document<\/a>, they detailed an unusual and complicated method for eliminating background magnetic interference \u2014 one they said was necessary for them to detect the tiny magnetic field rejected by the small sample. This method was inconsistent with how they\u2019d described the procedure in the original paper, which led Nature <\/em>to issue a retraction last September.<\/p>\n Hirsch and other physicists allege that the misconduct goes beyond a misleading mix-up regarding the magnetic background. In September, Hirsch and Dirk van der Marel<\/a>, a professor emeritus at the University of Geneva, published a claim<\/a> that what Dias and Salamat had released as raw CSH data was actually derived from the published data. \u201c[We] proved basically mathematically that the raw data are not measured in the laboratory; they are fabricated,\u201d Hirsch said. Hamlin independently released a preprint<\/a> last October claiming that the electrical resistivity data also appeared to have been processed in an undisclosed manner \u2014 a new allegation atop the issue that led to the 2022 retraction.<\/p>\n<\/div>\n <\/br><\/br><\/br><\/p>\n
\nRoom-Temperature Superconductor Discovery Meets With Resistance<\/br>
\n2023-03-09 21:58:15<\/br><\/p>\nHitting All the Benchmarks<\/strong><\/h2>\n
A Troubled History<\/strong><\/h2>\n