The result of a group of physicists at the University of Rochester was featured on the cover of the journal Nature. They claimed to have found a room-temperature superconductor that does not require cooling systems. Although it was just a speck of carbon, sulfur, and hydrogen forged under extreme pressures, the hope was that the material would lead to variants that would enable lossless electricity grids and inexpensive magnets for magnetic resonance machines.
The result is no longer faith in. The study was withdrawn by Nature due to data issues other scientists have raised over the past two years that have undermined confidence in one of two key signs of superconductivity. James Hamlin is an experimental Condensed Matter physicist at the University of Florida. The University of California, San Diego (UCSD) has been a critic of the study for a long time. He thinks it ignores evidence of scientific wrongdoing. He thinks this is a problem. It cannot be left as a difference of opinion.
Nature editors took the step over the objections of all the authors of the paper. The work has been verified and stood by. The most important part of any superconductivity claim is the drop in electric resistance, according to Ashkan Salamat, a physicist at the University of Nevada, Las Vegas. He said they were confused and disappointed in the decision-making.
The excitement builds for the class of materials called hydrides, which include the carbonaceous sulfur hydride developed by the team. It is thought that hydrogen behaves like a metal under higher pressures. Adding other elements to the hydrogen can increase the "chemical pressure," reduce the need for external pressure and make superconductivity reachable in small laboratory vises. Lilia Boeri, a theoretical physicist at the Sapienza University of Rome, says that these hydrides are a kind of realization of metallic hydrogen at slightly lower pressure.
The first superconducting hydride, a mix of hydrogen and sulfur that exhibited a sharp drop in electrical resistance at a critical temperature, was reported in 2015. It was a bit warmer than the Tc for most superconducting materials. Adding a third element to the mix was thought to allow researchers to get closer to ambient pressures. In order to make a new substance in the 2020 Nature paper, Dias and colleagues added carbon, crushed the mix in a diamond anvil cell, and heated it with a laser. The tests showed a drop in resistance at a Tc of about 15C and a pressure of about 25% of the pressure at the center of the Earth.
A drop in resistance alone is not enough in a field where many claims have come and gone. One of the key attributes of superconductors is their ability to expel a magnetic field when they cross Tc. It's impractical to measure the effect in a diamond anvil cell. They have to contend with tiny wires and samples, immense pressures, and a background magnetic signal. Hamlin says it's like you're trying to see a star when the sun isn't shining.
Magnetic susceptibility data was what led to the retraction. The team members did not include raw data after they subtracted a background signal. Critics complained that the team used a "user-defined" background rather than a measured one. In high-pressure physics, relying on a user-defined background is a common practice.
The paper was posted to the arXiv physics preprint server. The data was supposed to explain how the background was taken out. Brad Ramshaw is a quantum materials physicist at Cornell University. The process of going from the raw data to the published data was not easy to understand.
The firebrand who has criticized other hydride claims made stronger accusations. The data presented by Dias and Salamat could be represented by a smooth curve, which is impossible in a lab. I think they're not real. There were suspicious similarities to data in a paper on superconductivity in europium. The study that shared one author with the Nature paper was withdrawn because of incorrect magnetic susceptibility data.
In February, he was temporarily banned from posting to arXiv after he continued to hammer on the Dias study. The University of Rochester found no evidence of scientific wrongdoing. The susceptibility data in the Dias study were found to be pathological by the two critics. Van der Marel is reassured by the Nature's reversal. He says it's good to know you're not the only one who believes something is wrong.
The raw data alone shows the change in magnetic susceptibility, according to Dias. They are not high-pressure experimentalists. He believes that some of their actions have turned into personal attacks. People won't throw mud at us from a distance. The department chair and dean at UCSD received letters from Dias.
According to Eremets, the study may still be correct. He has tried many times to duplicate the results. The basics of the experimental protocol have been shared, but Eremets says they have been less forthcoming in the details. "Borai agrees." She says that there are a lot of people who are more careful.
People are welcome to come to their labs and look at their methods. There is an open door policy. He points to the July publication of a copy of the novel. Critics question its independence because it was led by a group that included many of the same people who wrote the Nature paper.
They are not stopping. Unearthly Materials is a company co-founded by the duo. There are claims of superconductivity in new hydride compounds. He said that they had moved on from the 2020 work. There is a new era of high- temperature superconductivity.
Eremets doesn't think that the new superconductors will stand up to scrutiny. How could this happen? He touches everything. He is confident that the patient work of science will sort out the questionable claims. He says that science isn't afraid of things. The truth will come soon.
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