It may be too soon to mourn the disappearance of a claim of room temperature superconductivity.
On September 26, the newspaper Nature retracted an article describing a material that seemed transform into a superconductor at a pleasant temperature of 15° Celsius (SN: 10/14/20). The notice shook many people on the ground. But a new experiment carried out just days after the retraction confirms the claim of a world temperature record, according to an eyewitness and others familiar with the experiment.
Superconductors carry electricity without resistance, which means they are useful for efficiently transmitting energy. They could save huge amounts of energy that is wasted in conventional metal wires. Currently, they are used to create powerful magnetic fields for medical imaging and particle physics experiments, as well as serving as components in high-performance circuits and even levitating high-speed trains. But to work, superconducting materials generally need to be cooled well below 0°C, and many to temperatures close to absolute zero, or -273°C.
When researchers announced in 2020 that a sample composed of hydrogen, sulfur and a little carbon became a superconductor at record temperatures, dreams of room-temperature superconductivity seemed about to come true. One of the problems was that the material had to be subjected to enormous pressures, around 2.6 million times atmospheric pressure – about the pressure found in parts of the Earth’s core. Still, the discovery hailed a potential scientific and technological revolution.
Over the next two years, controversy swirled around the report. The maelstrom centers on how researchers prepared and processed data that showed changes in a magnetic property known as susceptibility. Ultimately, the publishers of Nature took the unusual step of retracting the paper despite scholars’ objections. “We have now established that certain key data processing steps … used a non-standard user-defined procedure,” the editors write at Nature in the withdrawal. “The details of the procedure were not spelled out in the article and the validity of the background subtraction was subsequently called into question.”
The new experiment is not a copy of the one reported in the retracted article, but the researchers replicated some of their research that raised red flags in the scientific community.
Ranga Dias, a University of Rochester physicist who led the research on the now retracted paper, led the new measurements at the Advanced Photon Source at Argonne National Laboratory in Lemont, Illinois. “We’ve been working on this experiment for almost six months, building and reconfirming the correct methodology,” Dias says. “I would say the data we got at Argonne is more compelling, not just comparable,” to the retraction data. Nature paper.
“The experiment took place over two days, September 27 and 28,” says physicist Nilesh Salke of the University of Illinois at Chicago, who was not affiliated with the original research. Salke’s role at Argonne was to probe a sample of the material in question with X-rays while it exhibited magnetic susceptibility associated with high-temperature superconductivity. “We saw the first signal of sensitivity on September 27, consistent with claims reported in the retract Nature paper.”
This latest twist is unlikely to end the controversy that accompanied the original claim, at least in the mind of University of California San Diego physicist Jorge Hirsch. Hirsch has been one of the most vocal critics of the claim of room temperature superconductivity.
“I didn’t know it would be retracted, but I was hoping it would be,” says Hirsch, who was not affiliated with either the original experience or the novella. He says he asked the authors for the raw data from the previous study a month after it was published, but was refused. “The authors said, ‘No, we can’t provide you with the data because our lawyers said it would affect our patent rights.'”
With the intervention of Nature, Hirsch finally got the numbers. What he saw disturbed him. Hirsch is skeptical of the possibility of high-temperature superconductivity in these types of hydrogen-based materials in general, but says he takes issue with how the data has been processed.
“There were real issues between the raw data and the published data,” says Hirsch. He believes that NatureRetraction doesn’t go far enough. “It’s not that the data wasn’t properly processed.” With physicist Dirk van der Marel of the University of Geneva, Hirsch dives into problems with data in an article published on September 15 in the International Journal of Modern Physics B. “Our analysis proves mathematically that the raw data was not measured in the laboratory. They were made.
Dias and his colleagues deny any irregularities in their data or analyzes and are moving forward with experiments like Argonne’s. But this work awaits peer review. For the moment, NatureThe retraction of reinforces existing doubts around superconductivity at room temperature.
“Ultimately, this all has to be validated by different groups who get the answer,” Hirsch says.