Facing a mutiny by his co-authors, Ranga Dias, the University of Rochester (U of R) physicist embroiled in controversy over his superconductivity research and allegations of scientific misconduct, is set to have a third paper retracted.
The paper, published on 8 March in Nature, made the stunning claim that Dias and his colleagues had discovered the first material that could conduct electricity without resistance at room temperatures and moderate pressures. Room-temperature superconductor claims stir excitement because of the potential applications, such as lossless electrical grids and powerful magnets for trains and medical imaging. If the paper is retracted, it will follow retractions of two other superconducting claims from Dias’s teams: one last month from Physical Review Letters (PRL), and one in September 2022 of a different Nature paper.
On 1 September, Nature attached an editor’s note to the March paper, warning readers that “the reliability of data presented in this manuscript is currently in question.” A week later, eight of the co-authors on the 11-person paper submitted a letter to Nature requesting the study be retracted, The Wall Street Journal first reported on Tuesday. Science has obtained the letter and additional documents, which raise concerns about the reliability of the data and Dias’s treatment of his co-authors. “We respectfully request and recommend that Nature issue a retraction,” conclude the signatories, who include five recent graduate students of Dias’s.
The documents indicate Nature plans to retract the paper. In a 14 September email to the co-authors, Nature Senior Editor Tobias Rödel says a postpublication review revealed issues that are “mostly unaddressed.” Rödel added, “We are in absolute agreement with your request that the paper be retracted.” Responding to Science through a spokesperson, Nature’s Chief Physical Sciences Editor Karl Ziemelis said the journal is “carefully” investigating concerns. “We expect to take action in the near future.”
In emails throughout the postpublication review process, Dias reiterated his “unwavering confidence in the integrity of our data.” He did not respond to a request for comment.
In the March paper, Dias and his colleagues announced that a compound of lutetium, nitrogen, and hydrogen (LuNH) superconducts at temperatures up to 294 K when squeezed to a comparatively moderate pressure of 10,000 atmospheres. (Dias had made earlier claims of creating materials that superconduct at close to room temperature, but only at pressures of more than 1 million atmospheres.)
Russell Hemley, a condensed matter physicist at the University of Illinois Chicago, has reported replicating the LuNH results using a sample shared by Dias. But Peter Armitage, a condensed matter physicist at Johns Hopkins University, says Hemley’s resistance measurements may be flawed, the result of electrical probes losing contact with the tiny sample. Hemley claims his measurements are reproducible, which he says “clearly shows that the resistance drops were intrinsic to the sample and did not arise from possible problems with contacts.” Meanwhile, dozens of other theoretical studies and experimental replication efforts have found overwhelming evidence against room-temperature superconductivity in LuNH.
Questions about the March paper’s results appeared online immediately after its publication. On 2 May, two researchers submitted an anonymous critique of the paper to Nature. These researchers disclosed their identities to Science: They are James Hamlin, a high-pressure experimentalist at the University of Florida, and Brad Ramshaw, an expert in superconductivity at Cornell University.
Hamlin and Ramshaw focused on data supporting the observation of zero electrical resistance, a hallmark of superconductivity. Although the paper presented figures showing the resistance dropping to about zero, the authors acknowledged modifying the data by subtracting a background signal. Background subtraction is sometimes done in high-pressure superconductivity studies, but the practice is controversial because it can give the false appearance of zero resistance.
In their critique, Hamlin and Ramshaw pointed out that the paper describes a background subtraction method that produces a resistance plot drastically different from the published version. On 28 May, Dias and the other senior author on the paper, Ashkan Salamat, a physicist at the University of Nevada, Las Vegas, provided Nature editors with updated instructions on the background subtraction method. But applying this method still produced a figure different from the published plot. Essentially, they could not explain how they arrived at a plot that showed zero resistance, Hamlin says. “The problem is they’re not able to answer the question of how much they subtracted off.”
In response to the critique, Nature initiated a postpublication review process, soliciting feedback from four independent experts. In documents obtained by Science, all four referees expressed strong concerns about the credibility of the data. “I fail to understand why the authors … are not willing or able to provide clear and timely responses,” wrote one of the anonymous referees. “Without such responses the credibility of the published results are in question.” A second referee went further, writing: “I strongly recommend that the article by R. Dias and A. Salamat be retracted.”
Most of the paper’s co-authors were not included in these initial deliberations until 6 July, at which point Dias provided them with a PDF of the postpublication peer review. In their letter to Nature the co-authors allege they had raised concerns about the study prior to publication, but that Dias dismissed them. They say Dias gave some of them an ultimatum: Remove their names from the paper or allow it to proceed. “Neither choice seemed tenable given that Dr. Dias was in control of our personal, academic, and financial circumstances,” they write. “We did not feel that we were able to speak freely.”
After seeing the postpublication review, the co-authors used their access to the raw data to corroborate Hamlin and Ramshaw’s concerns about the zero-resistance measurement. They found that the paper relied on a method to determine the resistance that was not discussed or disclosed to the co-authors and did not match the raw data. They also argued that another key piece of data presented as evidence of superconductivity, the heat capacity of the sample, was a “flawed measurement.”
“There are not many new facts in the big picture, but the brazenness and/or incompetence is remarkable,” says Armitage, who reviewed the findings by the postpublication reviewers and in the co-author letter.
Before the co-authors sent their letter to Nature, Dias sent a cease-and-desist letter to six of them—five of his former graduate students and one U of R faculty member. He warned them about the “potential legal consequences of your actions and to consider the ethical implications of making baseless allegations against a colleague and fellow scientist.” Dias has previously sent cease-and-desist letters to other critics of his work. “Raising concerns about data and processes is an integral part of our scientific practice,” says Shanti Deemyad, a condensed matter physicist at the University of Utah. “The students are courageous for voicing their concerns and doing the right thing, and the scientific community should protect them.”
All co-authors signed the letter to Nature, except Dias and two of his U of R students. The signatories also include Salamat, a longtime collaborator who with Dias co-founded a spinoff company, Unearthly Materials, to commercialize superconductors. Earlier this year, during PRL’s investigation of its now-retracted paper, Salamat provided what the journal concluded was false raw data in “a deliberate attempt to obstruct the investigation.” Salamat did not respond to requests for comment.
Dias is also under investigation by his alma mater, Washington State University, for allegedly plagiarizing more than 20% of his Ph.D. thesis. He has previously claimed to be “addressing these issues directly with his thesis adviser.” U of R had already conducted two internal investigations of Dias’s research that it says found no evidence of misconduct. However, a U of R spokesperson says a third investigation is now underway by external experts who are looking into “the integrity of data across multiple papers.”
