Weird Science | Why claims of room-temperature superconductivity are often controversial

The hunt for a superconductive material at room temperature remains alluring and has given rise to many claims which have, however, been subsequently disproved

Over the last few years, the scientific community has keenly followed a number of claims about superconductivity having been achieved at room temperature. That is a Holy Grail of science, because superconductivity, a property that enables some materials to conduct electricity at zero resistance but is known to occur only at extremely low temperatures, would revolutionise the power transmission industry if it happened at ambient temperature.

A magnet floats above a superconductor cooled with liquid nitrogen.(University of Rochester)

All such claims, however, have since come under a cloud. One, made by South Korean scientists, subsequently failed tests conducted by other researchers seeking to replicate the claimed results. Two, claims made by another team have both been controversial, with the latest reportedly disowned by team members.

Ranga P Dias of the University of Rochester led a team of 11 scientists who published their results in Nature in March this year; now, eight of these authors have asked the journal to retract the paper, the Wall Street Journal reported.

Before that, in 2020, Dias and colleagues had published another paper in Nature describing a different material that could supposedly superconduct at room temperature. Nature retracted that paper in 2022 after other scientists raised red flags.

What these claims and controversies underline is the allure of room-temperature conductivity and the difficulty in actually achieving it.

The Holy Grail

Electricity flowing through any material encounters resistance, a property that opposes the flow. This results in part of the electrical energy being lost in the form of heat. Superconductivity, discovered in 1911, raised an intriguing prospect: At extremely cold temperatures, some materials could conduct electricity without facing resistance. This brought the promise of transmitting electricity without losses (in theory) or at least cutting down these losses drastically.

The hitch, however, has been the low temperatures involved, and the impracticability of replicating those in actual transmission infrastructure.

For example, mercury and tin have zero electrical resistance at about –269°C, and lead at –266°C.

“Room-temperature superconductivity has been a dream of the scientific community since the discovery of the phenomenon in 1911. If this happens at room temperature and ambient conditions, it will revolutionise the whole electronics industry and the power sector, with the lossless transmission of electricity from one terminal to another,” said Dr VPS Awana, chief scientist at the Council of Scientific and Industrial Research’s National Physical Laboratory (CSIR-NPL).

“It is this urgency that keeps condensed matter experimental physicists and material scientists on their toes to discover an ambient-condition, room-temperature superconductor,” Awana added.

A number of researchers, however, sometimes jump the gun and report results that are not reproduced by independent researchers, Awana said. His group at CSIR-NPL was among the first teams who tested the Korean researchers’ recent claims about their material, called LK-99, which was supposedly superconductive at room temperature and ambient pressure. They found that it does not show any signature of superconductivity at room temperature.

The claims about LK-99 were published on a preprint. The two controversial claims by Ranga Dias and colleagues, on the other hand, both passed peer review and were published in Nature before running into separate controversies.

Ranga Dias led the team that claimed the material LuNH was superconductive at room temperature; eight of his co-authors have now sought retraction of the paper.(University of Rochester )

The twin claims

In their paper in Nature in 2020, the Rochester University team described a material called carbonaceous sulphur hydride (CSH) as being superconductive at room temperature. In 2022, physicists Jorge E Hirsch and Dirk van der Marel raised issues about CSH in the International Journal of Modern Physics B. “What led to the retraction I think are the issues we raised about data manipulation and fabrication,” Hirsch told HT in March this year.

That month, Dias and colleagues published their second paper describing a compound called lutetium nitrogen hydride (LuNH) which, they said, exhibits superconductivity at about 21°C. The scientific community, however, greeted the claim with a degree of scepticism given the previous paper.

Then, the fresh controversy broke earlier this month.

According to the WSJ, eight of the authors have written to Nature seeking that the paper be retracted because Dias had misrepresented data. Dias, who had discussed both materials with HT in March, did not respond to a mail about the latest controversy.

Hirsch, who is affiliated with the University of California, San Diego, remains as critical as ever. He noted that all co-authors share the responsibility that the experimental results presented in the paper represent accurately what was measured.

“As reported in The Wall Street Journal, several of the co-authors of the 2023 Nature paper reporting room temperature superconductivity in LuNH have taken this responsibility seriously, and that is commendable particularly since often it doesn’t happen. I believe the journal should follow the request and recommendation of these co-authors to retract the paper,” Hirsch told HT.

“Independently, I have found several reasons for concern that indicate to me that the measurements reported for LuNH do not originate in superconductivity, and I understand many other researchers also found strong evidence that disproves the claim that LuNH is a superconductor,” he said.

Dias’ other controversies

Between the last paper in Nature and the fresh concerns raised, Dias has been at the centre of at least two other controversies, neither of them related to superconductivity. In August this year, Physical Review Letters retracted a paper by Dias and colleagues citing concerns over data integrity; this was about the electrical properties of manganese disulphide.

The other controversy around Dias involves allegations of plagiarism. His PhD thesis of 2013 at Washington State University was found to contain many passages identical to a 2007 thesis by James Hamlin at Washington University in St Louis, according to reports in Nature magazine (which works independently of the journal), Science and Physics Magazine. Hamlin found the identical passages using a plagiarism checker.

Kabir Firaque is the puzzles editor of Hindustan Times. His column, Weird Science, tackles a range of subjects from the history of inventions and discoveries to science that sounds fictional, but it isn't.