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Recent theoretical predictions have shown that a new class of materials based on superconducting hydrides could pave the way for higher temperature superconductivity. Researchers at the Max Planck Institute of Chemistry in Germany have teamed up with researchers at the University of Chicago to create one of these materials, lanthanum superhydrides, to test their superconductivity and determine its structure and structure. composition.
The only problem was that the material had to be subjected to extremely high pressure – between 150 and 170 gigapascals, more than a million and a half of the pressure at sea level. It's only in these conditions of high pressure that the material – a tiny sample of only a few microns – showed superconductivity at the new record temperature.
In fact, the material had three of the four characteristics necessary to prove superconductivity: it lost its electrical resistance, decreased its critical temperature under an external magnetic field and showed a change of temperature when certain elements were replaced by different isotopes. The fourth characteristic, called the Meissner effect, in which the material expels any magnetic field, has not been detected. This is because the material is so small that this effect can not be observed, according to the researchers.
They used Argonne National Laboratory's advanced photon source, which provides high-energy, high-gloss X-ray beams that have made breakthroughs in many areas, from better batteries to deeper understanding of the interior. from Earth, to analyze the material. During the experiment, researchers at the Center for Advanced Radiation Sources at the University of Chicago pressed a small sample of the material between two tiny diamonds in order to exert the necessary pressure, then used the X-rays of the beam to probe its structure and composition.
Since the temperatures used to conduct the experiment are in the normal range of many places in the world, the ultimate goal of ambient temperature – or at least 0 degrees Celsius – seems to be within our reach.
The team is already pursuing its collaboration to find new materials capable of creating superconductivity under more reasonable conditions.
"Our next goal is to reduce the pressure needed to synthesize samples, bring the critical temperature closer to room temperature, and perhaps even create samples that can be synthesized at high pressures, but still superconducting at normal pressures." said Prakapenka. "We continue to search for new and interesting compounds that will bring us new discoveries, often unexpected."
Quote: "Superconductivity at 250 K in high pressure lanthanum hydride". Drozdov et al., Nature, May 23, 2019. Doi: 10.1038 / s41586-019-1201-8
Funding: Department of Energy, National Science Foundation
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