Scientists this week announced a tantalizing advance that fulfills the dream of a material that can transmit electricity effortlessly under everyday conditions. Breakthroughs like this could transform nearly every technology that uses electricity, opening up new possibilities for your cell phone, maglev trains and future fusion power plants.
Normally, the current encounters resistance as it travels through the wire, almost like a friction, and some energy is lost as heat. A century ago, physicists discovered materials now known as superconductors, in which electrical resistance seemed to magically disappear. But these materials only lose their resistance at supernaturally low temperatures, which limits practical applications. For decades, scientists have been searching for superconductors that work at room temperature.
This week’s announcement is the latest attempt at that, but it comes from a team facing widespread skepticism after a 2020 paper described a promising but less practical superconducting material retract After other scientists questioned some of the data.
The new superconductor consists of lutetium, a rare earth metal, and hydrogen mixed with a small amount of nitrogen. It needs to be compressed to a pressure of 14,500 pounds per square inch before it can become superconducting. That’s about 10 times the pressure exerted on the bottom of the ocean’s deepest trenches.
But that’s also less than one percent of what the 2020 results called for, which is similar to the crushing forces found thousands of miles deep inside the Earth. This suggests that further research into the material could lead to superconductors operating at ambient room temperature and the usual atmospheric pressure of 14.7 pounds per square inch.
“This is the beginning of a new class of materials that can be used in practical applications,” Ranga P. Dias, a professor of mechanical engineering and physics at the University of Rochester in New York, told a room full of scientists Tuesday in Las Vegas. Gasth meeting of the American Physical Society.
A fuller account of his team’s findings Published Wednesday in Naturethe same journal that published it, then retracted its 2020 findings.
Rochester’s team started with a small, thin foil of lutetium, a silvery-white metal that is the rarest of the rare earth elements, and pressed it between two interlocking diamonds. A gas containing 99 percent hydrogen and 1 percent nitrogen is then pumped into the small chamber and compressed to high pressure. The samples were heated overnight at 150°F, and after 24 hours, the pressure was released.
About a third of the time, the process produced the expected result: a small, vibrant blue crystal. “Doping nitrogen into lutetium hydride is not so easy,” said Dr. Dias.
In one of the University of Rochester lab rooms used by Dr Dias’ group, graduate student Hiranya Pasan demonstrated the material’s surprising color-changing properties during a reporter interview last week . The blue turned red as the screw was tightened to increase the pressure.
“It’s very pink,” says Dr. Dias. If the pressure is higher, “it turns bright red,” he said.
Shining laser light through the crystals revealed how they vibrate and unlocked information about the structure.
In another room, other members of Dr Dias’ team are taking magnetic measurements of other crystals. As the temperature dropped, the expected curve appeared in the data plotted on the computer screen, indicating a transition to a superconductor.
“This is a real-time measurement that we’re doing now,” Dr. Dias said.
In the paper, the researchers report that the pink crystals exhibit key properties of superconductors, such as zero electrical resistance, at temperatures as high as 70 degrees Fahrenheit.
“I’m cautiously optimistic,” says Timothy Strobel, a scientist at the Carnegie Institution of Science in Washington, who was not involved in Dr. Dias’ research. “The data in the paper looks good.”
“If this is true, it would be a very important breakthrough,” said Paul CW Chu, a professor of physics at the University of Houston, who was also not involved in the research.
However, the “what if” part of the sentiment revolves around Dr Dias, who has been plagued by skepticism and criticism, with some scientists even accusing him of falsifying some of the data. The results of the 2020 paper in the journal Nature have not been replicated by other research groups, and critics say Dr Dias has been slow to get others to examine his data or conduct an independent analysis of his superconductor.
Last year, the editors of Nature retracted the earlier paper, over the objections of Dr Dias and other authors.
“I lost some trust in that group’s work,” said University of Florida physics professor James Hamlin.
Still, the new paper passed the peer review process at the same journal.
“The retraction of a paper does not automatically disqualify an author from submitting a new manuscript,” said a Nature spokeswoman. “All submitted manuscripts are independently considered for their scientific quality and timeliness.”
At the conference in Las Vegas on Tuesday, many physicists packed a cramped conference room, and the moderator asked some to leave so they would not have to cancel the presentation. Once the room was sparse, Dr Dias was able to present his findings undisturbed. As he thanked the crowd, the host expressed regret that they didn’t have time to ask questions.
Dr. Strobel acknowledges the ongoing controversy surrounding Dr. Dias and the earlier remarkable claims that have yet to be reproduced.
“I don’t want to read too much into it, but there may be a pattern of behavior here,” Dr. Strobel said. “He could really be the best high-pressure physicist in the world and hopefully win a Nobel Prize. Or something else will happen.”
under pressure
Dutch physicist Heike Kamerlingh Onnes and his team discovered superconductivity in 1911. Not only do superconductors carry electricity with essentially zero resistance, but they also have a strange ability known as the Meissner effect, which ensures that the magnetic field inside the material is zero.
The first known superconductor required a temperature just 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 become superconducting in colder conditions than those encountered in everyday use.
The standard theory to explain superconductivity predicts that if hydrogen can be squeezed large enough, it should be a superconductor at higher temperatures. But even the toughest diamonds can crack before reaching such enormous pressures. Scientists began studying hydrogen mixed with another element, speculating that chemical bonds might help compress hydrogen atoms.
In 2015, physicist Mikhail Eremets at the Max Planck Institute for Chemistry in Mainz, Germany, reported that hydrogen sulfide—a molecule made up of two hydrogen atoms and one sulfur atom—is compressed to about 22 million atoms. It becomes superconducting in pounds per square inch at minus 94 degrees Fahrenheit. This was a record high temperature for a superconductor at the time.
Dr. Eremets and other scientists then discovered that lanthanum hydride, a compound containing hydrogen and lanthanum, achieves a superconducting temperature of minus 10 degrees Fahrenheit at ultrahigh pressures.
controversial conclusion
In the research described in the retracted paper in 2020, Dr Dias’ team used hydrogen, sulfur and carbon. With the three elements, the scientists say, they were able to tune the electronic properties of the compound to achieve higher superconducting temperatures.
However, not everyone is convinced of this.
Dr Diaz’s main rival is Jorge Hirsch, a theoretical physicist at the University of California, San Diego. He focused on measurements made by Dr Dias’ group of the carbon-sulfur-hydrogen compound’s response to an oscillating magnetic field, evidence of the Meissner effect. The plots in the paper seem so tidy that the scientists didn’t explain how they subtracted background effects in the plots.
Dr. Hirsch said that when Dr. Dias released the underlying raw data, his analysis showed it was generated by a mathematical formula that could not actually be measured in an experiment. “From measurements, you don’t get analytical formulas,” Dr. Hirsch said. “You get numbers with noise.”
His complaints about Dr. Dias became so tenacious and pointed that others in the field circulated a letter complaining about Dr. Hirsch’s decades of sabotage.
Dr. Hirsch, a bullish contrarian in the China store, is targeting the BCS theory, developed by three physicists—John Bardeen, Leon N. . Cooper and J. Robert Schrieffer in 1957 to explain how superconductivity works. He said the BCS was “a lie” in many ways and could not account for the Meissner effect. He offers his own alternative explanation.
Remarkably, Dr. Hirsch has been saying that it is impossible for any of these high-pressure materials to be superconductive, because hydrogen cannot be a superconductor. He has gained few allies.
While Dr. Hirsch is careful to say that scientists other than Dr. Dias did not misbehave, he says they are deluding themselves.
“In my opinion, garbage becomes the conclusion,” he said.
resistance and reproduction
Dr. Hamlin of the University of Florida also delved into the magnetic measurements and said the raw data looked more like it came from published data than the other way around.
Dr. Hamlin was also disturbed when he discovered that several sentences from a doctoral thesis he wrote in 2007 appeared verbatim in Dr. Dias’ thesis.
Dr Dias dismissed the ongoing criticism and said his team offered an explanation. “I just thought it was just background noise,” he said. “We strive to continually push our science forward.”
He said he still stands by the earlier results, and that Wednesday’s paper uses a new magnetic measurement technique. The paper has gone through five rounds of reviewers, and all raw data supporting the findings are being shared, he said.
“It came back to nature,” Dr. Dias said. “So that tells you something.”
University of Rochester spokeswoman Sara Miller said that after two university investigations, it “determined that there was no evidence to support these concerns.” She also said the university “considered withdrawing the Nature paper in September 2022.” paper and came to the same conclusion.”
For sentences copied from Dr. Hamlin’s doctoral dissertation, Dr. Dias said he should have included citations. “It was my mistake,” Dr. Dias said.
Preprint redoing measurements of sulfhydryl materials Papers from the 2020 retraction are now circulating, but even this raises questions. “They are very different from the original measurements,” Dr. Strobel said. “Some might say they haven’t even reproduced the results themselves.”
Since the new lutetium-based material is superconducting at much lower pressures, many other research groups will be able to try to reproduce the experiment. Dr Dias said he would like to have a more precise recipe for how to make the compound and share samples, but intellectual property rights need to be addressed first. He founded a company called Unearthly Materials with a plan to turn the research into profit.
Dr. Strobel said he would get back to work as soon as he returned from the Las Vegas meeting. “We can have results within a day,” he said.
Dr. Hirsch also said he hopes answers will come soon. “If that’s true, it proves my work for the past 35 years wrong,” he said. “I’ll be happy because I’ll know.”
Dr Hirsch added, “But I think I’m right, it’s wrong.”
Kimberly McGee Reporting from Las Vegas.
