Physicists at the University of Leipzig have once again gained a deeper understanding of the mechanism behind superconductors. This brings the research group led by Professor Jürgen Haase one step closer to their goal of developing the foundations of a theory for superconductors that would allow current to flow without resistance and without energy loss. The researchers found that in superconducting copper-oxygen bonds, called cuprates, there must be a very specific charge distribution between copper and oxygen, even under pressure.
This confirmed their own findings in 2016, when Haase and his team developed an experimental method based on magnetic resonance that can measure changes that are relevant for superconductivity in the structure of materials. They were the first team in the world to identify a measurable material parameter that predicts the maximum possible transition temperature—a necessary condition to achieve superconductivity at room temperature. Now they have found that cuprates, which under pressure enhance superconductivity, follow the charge distribution predicted in 2016. The researchers published their new findings in the journal. PNAS.
“The fact that the transition temperature of cuprates can be enhanced under pressure has puzzled researchers for 30 years. But until now we didn’t know which mechanism was responsible for this,” Haase said. He and his colleagues at the Felix Bloch Institute for Solid State Physics are now much closer to understanding the actual mechanism of these materials.
“At the University of Leipzig, with the support of the Graduate School of Molecules and Nano-objects (BuildMoNa) – we established the basic conditions necessary to research cuprates using nuclear resonance, and Michael Jurkutat was the first PhD researcher to join us. Together, we established the Leipzig Relation, which says that you have to take electrons from the oxygen in these materials and give them to the copper to raise the transition temperature. You can do this with chemistry, but also with pressure. But hardly anyone would have thought that I could measure all of this with nuclear resonance,” Haase said.
Their current discovery could be just what is needed to produce a superconductor at room temperature, which has been the dream of many physicists for decades and is now expected to take only a few years, according to Haase. Until now, this has only been possible at very low temperatures, around minus 150 degrees Celsius and below, which are not easily found anywhere on Earth. About a year ago, a Canadian research group verified the findings of Professor Haase’s team in 2016 using newly developed computer-aided calculations and thus substantiated the findings theoretically.
Superconductivity is already used today in a variety of ways, for example in magnets for MRI machines and in nuclear fusion. But it would be much easier and less expensive if superconductors worked at room temperature. The phenomenon of superconductivity was discovered in metals as early as 1911, but even Albert Einstein did not try to come up with an explanation back then. Almost half a century passed before the BCS theory provided an understanding of superconductivity in metals in 1957. In 1986, the discovery of superconductivity in ceramic materials (cuprous superconductors) at much higher temperatures by physicists Georg Bednorz and Karl Alexander Müller raised new questions, but also raised hopes that superconductivity could be achieved at room temperature.
Michael Jurkutat et al., How Pressure Raises the Critical Temperature of Superconductivity in YBa 2 Cu 3 O 6+ y, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2215458120
Provided by Leipzig University
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