Tuesday, March 14, 2023

Evidence of near-ambient superconductivity in a N-doped lutetium hydride


The absence of electrical resistance exhibited by superconducting materials would have enormous potential for applications if it existed at ambient temperature and pressure conditions. Despite decades of intense research efforts, such a state has yet to be realized.

Here we report evidence of superconductivity on a nitrogen-doped lutetium hydride with a maximum Tc of 294 K at 10 kbar, that is, superconductivity at room temperature and near-ambient pressures. [Superconductivity was verified via] temperature-dependent resistance with and without an applied magnetic field, the magnetization (M) versus magnetic field (H) curve, a.c. and d.c. magnetic susceptibility, as well as heat-capacity measurements.

The Independent:  

Scientists have discovered a new material that could be set to change the entire world. Researchers say they have created a superconducting material that works at both a temperature and a pressure low enough to actually use it in practical situations.

Professor Dias and the team made the material by taking a rare earth metal named lutetium and mixed it with hydrogen and a small part of nitrogen. They were then left to react for two or three days, at high temperatures.

To work, the material still requires being heated to 20.5 degrees Celsius and compressed to about 145,000 psi. But that is vastly less intense than other, similar materials – including those announced in 2020 by Professor Dias that brought excitement and scepticism from scientists.

Wall Street Journal:

U.S. scientists say they have produced the first commercially accessible material that eliminates the loss of energy as electricity moves along a wire, a breakthrough that could mean longer-lasting batteries, more-efficient power grids and improved high-speed trains.

New York Times

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...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. 

“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.

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.

“I’m cautiously optimistic,” said Timothy Strobel, a scientist at the Carnegie Institution for Science in Washington who was not involved in Dr. Dias’s study. “The data in the paper, it looks great.”

This is a very exciting and potentially game-changing result. The hunt for a room-temperature superconductor has been frantic and long-lasting, due to properties that would enable them to revolutionize many aspects of modern technology. For its part, the paper is detailed and seems to have taken great care to demonstrate superconductivity via multiple channels. There is some controversy surrounding the results, which can be separated into two categories:

  1. Concerns about the validity of the results. Are they reproducible, or was this a fluke event? Is the new material really stable enough at STP to be viable?
  2. Ethical concerns about the results. The particular research group that put out this astonishing result has had a fraught past, with retracted papers and extended drama over previous results in a similar vein. Additionally, arguably the largest fraudulent scandal in scientific history (the infamous Schön scandal) was focused on this subfield, which tends to attract grandiose and wild claims.
For such a claim, one might expect jubilation and animated questions, but the audience’s response was hesitant—a few people politely asked technical questions, such as how well Dias’ team could control the amount of nitrogen in the sample. There was no whooping or cheering. The audience had been here before.

In 2020, Dias’ team announced in a paper in Nature that they had created a material, carbonaceous sulfur hydride, that superconducted at 287 K and 267 GPa. Researchers and news outlets lauded the finding, but the paper was retracted two years later after outside researchers found oddities in the results.

Another part of that wariness arises because, to date, no one has independently reproduced Dias’ team’s results. This lack of verification was raised by Jorge Hirsch of the University of California, San Diego, in the last talk of the session in which Dias and his team spoke. 


While the announcement has been greeted with enthusiasm by some scientists, others are far more cautious, pointing to the research group’s controversial history of alleged research malfeasance. (Dias strongly denies the accusations.) 

But incidents involving the team’s previous work — including but not limited to a near-room-temperature superconductivity claim published in Nature in 2020 and retracted late last year — have cast a shadow across today’s announcement. “It’s hard to not wonder if some of the same problems that have gone unaddressed in previous work also exist in the new work,” Hamlin said. 

“There is a lot of evidence for superconductivity here if you take it at face value,” said Jorge Hirsch, a physicist at the University of California, San Diego. “But I do not believe any of what these authors say. I am not sold at all.”

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...Almost immediately, a handful of experts spotted unusual patterns in the data used to verify the material’s response to magnetic fields. When [they] released their raw data a year later in the form of a 149-page document, they detailed an unusual and complicated method for eliminating background magnetic interference — 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’d described the procedure in the original paper, which led Nature to issue a retraction last September. 

Hirsch and other physicists allege that the misconduct goes beyond a misleading mix-up regarding the magnetic background. In September, [they] published a claim that what Dias and Salamat had released as raw CSH data was actually derived from the published data. “[We] proved basically mathematically that the raw data are not measured in the laboratory; they are fabricated,” Hirsch said. Hamlin independently released a preprint last October claiming that the electrical resistivity data also appeared to have been processed in an undisclosed manner — a new allegation atop the issue that led to the 2022 retraction.     

Yet the CSH paper isn’t the only related work under fire. One co-author of the CSH paper, Mathew Debessai, was the first author on a 2009 study claiming superconductivity in a third material, europium, which was later retracted for presenting altered data...Others have also argued that some of the data in another of Dias’ recent papers was duplicated from data taken while the team was studying a completely different substance.

Here is a figure summarizing the data believed to be duplicated. The zoom-ins to below the 120 K range look remarkably similar. 


Figure 2: Comparison of data on GeS and corresponding data purportedly measured on MnS... However, if we restrict our view to only the data below 120 K (right panels), we find that the data are essentially identical, within the precision of the extraction process. No transformations have been applied to the data. 

Considering only the data below 120 K, there is essentially perfect agreement of the shapes of three different pairs of curves within the limitations of the digitization methods. It can not be reasonably concluded that this could occur by coincidence across three different data sets appearing in two different figures. Can the authors please check if an error led to the GeSe data being used in the MnS paper? 

A big problem with confirming their results is that it can be challenging to ensure a recipe is followed exactly. Confirmation could be provided if Dias and his team shared the actual material, but they are unwilling to do so for proprietary reasons.


To solve the riddle, the U of R team “should do everything they can to help other groups reproduce it,” says Mikhail Eremets, a physicist at the Max Planck Institute for Chemistry, whose team discovered the first hydride superconductor in 2015 but failed to replicate the CSH results. “If they will not it will be a disaster.” But this level of cooperation doesn’t appear to be in the cards. Dias says Unearthly Materials, a company he and Salamat founded, is trying to commercialize the new hydride. “We are not going to distribute this material considering the proprietary nature of our process and the intellectual property rights that exist,” Dias said via email.

Other physicists aren’t pleased. “It’s a completely unscientific behavior,” Boeri says. Hamlin says he won’t commit a student to replicating the work unless the U of R group shares samples and raw data. Salamat says the raw data are available online. As for sharing samples, the paper provides a detailed recipe, he says. “People can go ahead and make it for themselves.” [emphasis added]

It's quite disappointing that they are unwilling to share the actual material, as that would silence most if not all of the controversy and let the discovery gain the prominence it deserves. Personally, I don't understand the difference between sharing the material for verification purposes versus sharing a detailed recipe that will allow for exact reproduction. This would be concerning regardless of the past history of the group. We've also seen this exact response from this group before: in 2020, when their last claimed room-temperature superconductor fell apart. It took a bit of digging, but I found Hirsch's original pre-print "Anatomy of a Probable Scientific Fraud". In it, he attaches emails he sent to Dias' team asking for access to their raw data, in order to help verify their results. 


It is also relevant to this story that independently Dr. Evgueni F. Talantsev had requested resistivity raw data as well as a a time track record for each measurement from Dias directly and through Nature editor Dr. Luke Fleet on October 21, 2020 [25] and again directly and through Nature editor Dr. Roedel on or about November 10. On November 16, Dias responded:

Dear Dr. Talantsev, We acknowledge your request for data relating to our recent Nature article entitled “Room temperature Superconductivity on carbonaceous sulfur hydrides”. We have discussed the request with counsel and unfortunately, we are not able to provide you with the data for a number of reasons, including the following. The data may contain patentable inventions for which patent applications have not been updated or filed. We have been advised that disclosure of the data may impair our ability to file patent applications in the future. We cannot anticipate when we may have the authorization to share the data. Regards, Ranga

This is the same justification they are using today to deny other researchers access to the material, for verification. As a reminder, the "patentable inventions" they used to justify the lack of transparency ended up falling through, as even their own analysis was unable to reproduce them:

New York Times:

A preprint redoing measurements of the carbon-sulfur-hydrogen material from the retracted 2020 paper is now circulating, but even that raises questions. “They’re significantly different from the original measurements,” Dr. Strobel said. “One could argue they haven’t even reproduced results themselves.”

Scientific American:

Hamlin went on to analyze a paper that Dias and Salamat published in Physical Review Letters (PRL) in 2021 in which they and their colleagues measured another hydride called manganese sulfide. Hamlin noted similarities between the electrical resistance data in the 2021 paper and those in Dias’s 2013 Ph.D. thesis, which had involved a completely different superconducting material. He shared these concerns with the journal and the paper’s authors. Salamat has since responded, suggesting that even though the two data sets may appear similar, the resemblance is not indicative of copied data. “We’ve shown that if you just overlay other people’s data qualitatively, a lot of things look the same,” he says. “This is a very unfair approach.”

This did not satisfy at least one of Salamat’s co-authors on the PRL paper: Simon A. J. Kimber, a former researcher, was disturbed to hear about the potential problem with the data and agrees with Hamlin’s conclusions. “I’ve been at this game for a long time, and I couldn’t think of a single reasonable explanation as to why those data sets should overlap like that,” he says. “I replied to everybody, to PRL’s editors, and said, ‘I think this should be retracted. I can’t think of any logical reason why this should be—retract, retract, retract.’” 

New York Times:

However, the “if” part of that sentiment swirls around Dr. 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 Dr. 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 Dr. Dias and the other authors.

“I’ve lost some trust in what’s coming from that group,” said James Hamlin, a professor of physics at the University of Florida.

Dr. Dias’s main antagonist is Jorge Hirsch, a theoretical physicist at the University of California, San Diego...The plot in the paper seemed too neat, and the scientists did not explain how they had subtracted out background effects in the plot. When Dr. Dias released the underlying raw data, Dr. Hirsch said, his analysis indicated that it had been generated by a mathematical formula and could not be actually measured in an experiment. 

I found this passage later in the article interesting (though admittedly not particularly relevant):

Dr. Hamlin was also disturbed when he found that several passages from his doctoral thesis, written in 2007, had appeared, word for word, in Dr. Dias’s dissertation...Of the copying of text from Dr. Hamlin’s doctoral thesis, Dr. Dias said he should have included citations. “It was my mistake,” Dr. Dias said.

Generally scientific writing is paraphrased for citation, not copied exactly. Even self-plagiarism is extremely discouraged, so I can't imagine any train of thought that would lead to actually copying someone else's work word-for-word in an original thesis. A citation arguably wouldn't have made that okay.

It is important to note that while Hirsch is not the only scientist to point out issues with the results (past and present) from Dias' team, he may have a bias as Dias' results would support a theory that he is somewhat infamous for opposing:


Ranga Dias, an applied physicist at the University of Rochester, who with his colleagues made the room-temperature superconductivity claim, rejects Hirsch’s allegations. He asserts that Hirsch isn’t an expert in high-pressure physics and that he has a history of claiming that the Nobel Prize–winning “BCS theory” underlying superconductivity is incorrect. Dias says Hirsch relentlessly badgers superconductivity researchers. “Hirsch is a troll,” Dias says. “We are not going to feed this troll” by providing the data. 

Dias and others say they don’t trust Hirsch to appraise the data fairly. “Unfortunately, sometimes he is not objective,” says Vasily Minkov, a chemist at the Max Planck Institute for Chemistry who synthesizes hydride superconductors and says Hirsch has cherry-picked data from the Max Planck experiments for his critiques.

This back-and-forth has resulted in moderation as the claims from each about the other have grown less and less professional.


A debate over claims of room temperature superconductivity has now boiled over into the realm of scientific publishing. Administrators of arXiv, the widely used physics preprint server, recently removed or refused to post several papers from the opposing sides, saying their manuscripts include inflammatory content and unprofessional language. ArXiv has also banned one of the authors, Jorge Hirsch, a theoretical physicist at the University of California, San Diego (UCSD), from posting papers for 6 months.

While Hirsch may have been somewhat abrasive (Daniel Arovas amusingly referred to the exchange as "distasteful accusations") he was far from the only person who shared the concerns--including some of the authors of the 2020 paper.

One of [the 2009] study’s authors, James Hamlin, a physicist now at the University of Florida, who participated in the europium study as a graduate student, recently determined, he says, that “there are alterations to the data.” The study’s senior author, James Schilling, an emeritus physicist at Washington University in St. Louis, says he shares that concern. Now, some of the co-authors are redoing the measurements, and if they don’t hold up, the team will retract the [2020] paper, Hamlin says. 

The paper was eventually retracted. 


Given the questions, several scientists say Dias should make his data public. “I am unhappy that Dias is supposedly not cooperating with researchers who are questioning his data,” says Marvin Cohen, a theoretical physicist at UC Berkeley. Schilling is blunt: “I told Dias to give [Hirsch] the raw data, for heaven’s sake.”

In his email [responding to Hirsch's request for the raw data], Dias wrote, “Given that you have an active comment on our work, we consider such a request would not be reasonable.” Frustrated, Hirsch requested the data from Nature and the National Science Foundation (NSF), which funded the work. On 30 August, Nature appended an editor’s note to Dias’s paper saying: “The editors of Nature have been alerted to undeclared access restrictions relating to the data behind this paper. We are working with the authors to correct the data availability statement.” NSF and the University of Rochester both tell Science they cannot comment on possible investigative matters.

A theoretical analysis on the theoretical feasibility of superconductivity in lutetium hydride was published. The results add an interesting dimension to the controversy.


Recently, room-temperature superconductivity has been reported in a nitrogen-doped lutetium hydride at near-ambient pressure [Dasenbrock-Gammon et al., Nature 615, 244 (2023)]. 

Here, we systematically study the phase diagram of Lu–N–H at 1 GPa using first-principles calculations, and we do not find any thermodynamically stable ternary compounds.

Our theoretical results show that the Tc values of N-doped LuH3 estimated using the Allen–Dynes-modified McMillan equation are much lower than room temperature.

The conclusion seems to be that, based on existing theory, it is not possible to form a stable combination of lutetium, nitrogen, and hydrogen. 

Notably, all predicted potential ternary compounds lie above the convex hull at 1 GPa. Thus, no ternary Lu–N–H compounds can remain thermodynamically stable at this pressure, which is consistent with the main results of Xie et al.26

And even if it were, it seems it would superconduct at far lower than room temperature, in line with existing experiments. 

Our simulations show that the lowest T_c is 4 K for LuH3 without doping. In addition, T_c increases with increasing N-doping concentration; thus, doping N atoms into LuH3 will increase T_c. However, the highest T_c in this VCA calculation is 22 K, obtained with 1% N-doping at 30 GPa, which is much lower than room temperature.

It's worth noting that 30 GPa is about 300 kbar, which is 30 times higher than the pressures reported in Dias et al. (2023). Further investigation is needed, but it seems theoretically unlikely to produce a material like the doped LuNH3 at the reported temperatures and pressures. Certainly even less likely for it to superconduct at room temperatures. This is based on existing theory, so the possibility remains that Dias et al. have discovered an exciting new effect that will require more advanced models to explain.

I've been posting occasional updates as I've followed this and other superconductor stories with great interest. This one took an interesting turn with a series of retractions from Nature.


RETRACTED ARTICLE: Room-temperature superconductivity in a carbonaceous sulfur hydride

The editors of Nature have been alerted to concerns regarding the manner in which the data in this paper have been processed and interpreted. Nature is working with the authors to investigate these concerns and establish what (if any) impact they will have on the paper’s results and conclusions. In the meantime, readers are advised to use caution when using results reported therein. 

This is their second retracted paper.

Nature News:

Nature has retracted a controversial paper claiming the discovery of a superconductor — a material that carries electrical currents with zero resistance — capable of operating at room temperature and relatively low pressure.

“They have expressed the view as researchers who contributed to the work 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 retraction report] says, adding that these co-authors “have concluded that these issues undermine the integrity of the published paper”.

“It is at this point hardly surprising that the team of Dias and Salamat has a third high-profile paper being retracted,” says Paul Canfield, a physicist at Iowa State University in Ames and at Ames National Laboratory. Many physicists had seen the Nature retraction as inevitable after the other two, and especially since The Wall Street Journal and Science reported in September that 8 of the 11 authors of the paper — including Salamat — had requested it in a letter to the journal.

One lab says it has partially reproduced Dias and Salamat’s results using a sample provided by the Rochester team. But many others, which tried creating their own samples and running tests, could not. And in the meantime, other causes for concern have arisen. An investigation launched by Physical Review Letters before it retracted its paper by Dias and Salamat found “apparent data fabrication”.


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.

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.

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.”

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.

In their letter to Nature the co-authors allege they had raised concerns about the study prior to publication, but that Dias dismissed them. 

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. 

New York Times:

A prominent physics journal on Tuesday retracted a materials science paper that has garnered scrutiny.

The retracted paper did not involve superconductivity, but it added to accusations against Dr. Dias of research misconduct, including the fabrication and falsification of data. 

Nine of the 10 authors of the paper, which was published in Physical Review Letters, agreed to the retraction. Dr. Dias was the lone holdout, and he has maintained that the paper accurately portrays the research findings. However, he said on Tuesday that his collaborators, working in the laboratory of Ashkan Salamat, a professor of physics at the University of Nevada, Las Vegas, introduced errors when producing charts of the data using Adobe Illustrator, software not typically used to make scientific charts.

This took me pretty massively by surprise. I can only speak from my own personal experience, but nobody--I mean nobody--makes charts by hand anymore. We've had programmatic tools to ensure precision for literally decades. Most plots these days are done using scripts that access plotting libraries; for example, I make my plots in Python using matplotlib. I just can't understand what part of the process one would use Adobe Illustrator of all things for--I wish Dr. Dias had elaborated on this more. The problems identified were found in the background subtraction procedure and potentially claims of duplicated data; without commenting on the truth of these allegations, how could one "accidentally" do these things or something similar in Adobe Illustrator of all things? And why would this affect the raw data files that were shared with the investigators and coauthors, which ultimately were found to be flawed as well? 

Nature News:

As part of the investigation, co-author Ashkan Salamat, a physicist at the University of Nevada, Las Vegas, and a long-time collaborator of Dias, supplied what he claimed was raw data used to create figures in the PRL paper. But all four investigators found that the data Salamat provided did not match the figures in the paper.

Ignoring everything else, the raw data didn't match the figures. But Dr. Dias necessarily needs the figures to be correct if his superconductor is legitimate--the figures showed the proof. 

Science News:

A stunning claim of a room-temperature superconductor that grabbed headlines has fizzled. The paper was retracted November 7 from the journal Nature, making for a trio of high-profile retractions for physicist Ranga Dias of the University of Rochester.

The retraction is no surprise to the scientific community, many of whom had expressed hefty skepticism about Dias’ work, following the earlier retractions and many other researchers’ failures to reproduce Dias’ results. 

Compared to the previous retractions, “this is much more worrying,” Boeri says. “This is not just somebody who is doing some honest mistakes.”

Ranga Dias (via Twitter):

Meissner effect on N- doped Lutetium Hydride! 

[mic drop gif]

The Meissner effect is considered the definitive proof of superconductivity!

I look forward to the submission of that result. At the end of the day, everyone only benefits if Dr. Dias is correct and room-temperature superconductivity is achieved.

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