Nature, one of the most prestigious journals in scientific publishing, on Tuesday retracted a high-profile paper it had published in March that claimed the discovery of a superconductor that worked at everyday temperatures.
It was the second superconductor paper involving Ranga P. Dias, a professor of mechanical engineering and physics at the University of Rochester in New York state, to be retracted by the journal in just over a year. It joined an unrelated paper retracted by another journal in which Dias was a key author.
Dias and his colleagues’ research is the latest in a long list of claims of room-temperature superconductors that have failed to pan out. But the retraction raised uncomfortable questions for Nature about why the journal’s editors publicized the research after they had already scrutinized and retracted an earlier paper from the same group.
A spokesperson for Dias said that the scientist denied allegations of research misconduct. “Professor Dias intends to resubmit the scientific paper to a journal with a more independent editorial process,” the representative said.
First discovered in 1911, superconductors can seem almost magical — they conduct electricity without resistance. However, no known materials are superconductors in everyday conditions. Most require ultracold temperatures, and recent advances toward superconductors that function at higher temperatures require crushing pressures.
A superconductor that works at everyday temperatures and pressures could find use in MRI scanners, novel electronic devices and levitating trains.
Superconductors unexpectedly became a viral topic on social networks over the summer when a different group of scientists, in South Korea, also claimed to have discovered a room-temperature superconductor, named LK-99. Within a couple of weeks, the excitement died away after other scientists were unable to confirm the superconductivity observations and came up with plausible alternative explanations.
Even though it was published in a high-profile journal, Dias’ claim of a room-temperature superconductor did not set off euphoria like LK-99 did because many scientists in the field already regarded his work with doubt.
In the Nature paper published in March, Dias and his colleagues reported that they had discovered a material — lutetium hydride with some nitrogen added — that was able to superconduct electricity at temperatures of up to 70 degrees Fahrenheit. It still required pressure of 145,000 pounds per square inch, which is not difficult to apply in a laboratory. The material took on a red hue when squeezed, leading Dias to nickname it “reddmatter” after a substance in a “Star Trek” movie.
Less than three years earlier, Nature published a paper from Dias and many of the same scientists. It described a different material that they said was also a superconductor although only at crushing pressures of nearly 40 million pounds per square inch. But other researchers questioned some of the data in the paper. After an investigation, Nature agreed, retracting the paper in September 2022 over the objections of the authors.
In August, the journal Physical Review Letters retracted a 2021 paper by Dias that described intriguing electrical properties, although not superconductivity, in another chemical compound, manganese sulfide.
James Hamlin, a professor of physics at the University of Florida, told Physical Review Letters’ editors that the curves in one of the paper’s figures describing electrical resistance in manganese sulfide looked similar to graphs in Dias’ doctoral thesis that described the behavior of a different material.
Outside experts enlisted by the journal agreed that the data looked suspiciously similar, and the paper was retracted. Unlike the earlier Nature retraction, all nine of Dias’ co-authors agreed to the retraction. Dias was the lone holdout and maintained that the paper accurately portrayed the research findings.
In May, Hamlin and Brad J. Ramshaw, a professor of physics at Cornell University, sent editors at Nature their concerns about the lutetium hydride data in the March paper.
After the retraction by Physical Review Letters, most of the authors of the lutetium hydride paper concluded that the research from their paper was flawed too.
In a letter dated Sept. 8, eight of the 11 authors asked for the Nature paper to be retracted.
“Dr. Dias has not acted in good faith in regard to the preparation and submission of the manuscript,” they told the Nature editors.
The writers of the letter included five recent graduate students who worked in Dias’ lab, as well as Ashkan Salamat, a professor of physics at the University of Nevada, Las Vegas, who collaborated with Dias on the two earlier retracted papers. Dias and Salamat founded Unearthly Materials, a company that was meant to turn the superconducting discoveries into commercial products.
Salamat, who was the company’s president and CEO, is no longer an employee there. He did not respond to a request for comment on the retraction.
In the retraction notice published Tuesday, Nature said that the eight authors who wrote the letter in September expressed the view that “the published paper does not accurately reflect the provenance of the investigated materials, the experimental measurements undertaken and the data-processing protocols applied.”
The issues, those authors said, “undermine the integrity of the published paper.”
Dias and two other authors, former students of his, “have not stated whether they agree or disagree with this retraction,” the notice said. A Nature spokesperson said they did not respond to the proposed retraction.
“This has been a deeply frustrating situation,” Karl Ziemelis, the chief editor for applied and physical sciences at Nature, said in a statement.
Ziemelis defended the journal’s handling of the paper. “Indeed, as is so often the case, the highly qualified expert reviewers we selected raised a number of questions about the original submission, which were largely resolved in later revisions,” he said. “This is how peer review works.”
He added, “What the peer-review process cannot detect is whether the paper as written accurately reflects the research as it was undertaken.”
For Ramshaw, the retraction provided validation. “When you are looking into someone else’s work, you always wonder whether you are just seeing things or overinterpreting,” he said.
The disappointments of LK-99 and Dias’ claims may not deter other scientists from investigating possible superconductors. Two decades ago, a scientist at Bell Labs, J. Hendrik Schön, published a series of striking findings, including novel superconductors. Investigations showed that he had made up most of his data.
That did not stymie later major superconductor discoveries. In 2014, a group led by Mikhail Eremets, of the Max Planck Institute for Chemistry in Germany, showed that hydrogen-containing compounds are superconductors at surprisingly warm temperatures when squeezed under ultrahigh pressures. Those findings are still broadly accepted.
Russell J. Hemley, a professor of physics and chemistry at the University of Illinois Chicago who followed up Eremets’ work with experiments that found another material that was also a superconductor at ultrahigh pressure conditions, continues to believe Dias’ lutetium hydride findings. In June, Hemley and his collaborators reported that they had also measured the apparent vanishing of electrical resistance in a sample that Dias had provided, and on Tuesday, Hemley said he remained confident that the findings would be reproduced by other scientists.
After the Physical Review Letters retraction, the University of Rochester confirmed that it had started a “comprehensive investigation” by experts not affiliated with the school. A university spokesperson said that it had no plans to make the findings of the investigation public.
The University of Rochester has removed YouTube videos it produced in March that featured university officials lauding Dias’ research as a breakthrough.