What happens to the superconductor at absolute temperature

Room temperature superconductivity: world record at 15 degrees

"At first I didn't believe in the result myself, but now we're sure," says Dias. Ultimately, the young assistant professor carried out the experiment more than 30 times, measuring the electrical resistance and the magnetic sense of the sample in each case. In doing so, he probably also wanted to prevent an experience from 2017 from happening again: At that time, together with his older colleague Isaac Silvera, he published information about a metallic phase of pure hydrogen, which would be something like the ultimate superconductor. Until today, however, the measurements from that time have not been reproducible, which has earned Dias and Silvera much criticism.

Express through peer review

This time things look better at first glance, confirm all of the experts contacted by Ā»Spektrum.deĀ«. The current publication also had to go fast: Because of the great competition in this area, he asked the specialist magazine "Nature" for an extra quick review, says Dias. He submitted the manuscript at the end of August. After that, it was just six weeks before the work was published - an unusually short period of time.

"It is difficult to imagine that a thorough peer review took place during this time," criticizes Graeme Ackland of the University of Edinburgh. At first glance, the study appears to be quite solid, but some important questions remain unanswered. Bernhard Keimer, Director at the Max Planck Institute for Solid State Research in Stuttgart, sees it similarly. "You don't really know what kind of material it is," he says.

So far it is completely unclear which lattice structure the sulfur, hydrogen and carbon atoms form in the tiny sample container of Dias and his team. With the previous record holder LaH10 was it different: Here calculations showed that the hydrogen atoms form a kind of cage around the heavier foreign atom. This creates a symmetrical lattice similar to that of metallic hydrogen.

Three is better than two

In the case of the complex of C, S and H atoms from Dias' experiment, on the other hand, something else is likely to favor superconductivity: the three elements may form extremely stable "covalent" bonds under pressure, which make the atomic lattice very rigid. This would allow vibrations to spread easily through the material, bringing electrons together to form Cooper pairs. At least that's how it works at H3S, which stood on the podium in 2015.

It remains to be seen whether this also explains the new record holder's superconductivity. Measurements in which X-rays are scattered by the sample could have provided information here, says Mainz competitor Mikhail Eremets. "It's a mystery why the team didn't publish such data."