Serious laboratories have begun to study the properties of the LK-99 material, in which South Korean scientists allegedly discovered superconductivity under room conditions. Nature published a note with a selection of references to such studies, during which scientists could not confirm the synthesis of LK-99 or its superconductivity.
Image Source: Adam Fenster/University of Rochester
The statement of South Korean researchers about the superconducting properties of the LK-99 material at room conditions became a network sensation. And no wonder! The phenomenon of superconductivity without extremely low temperatures and exorbitant pressures can change many aspects of our lives, from providing electricity to urban consumers, where energy losses are enormous and they are constantly growing as the load increases (hello to electric vehicles) and ending with hand-held MRI scanners or compact thermonuclear reactors.
The first attempts to reproduce LK-99 did not allow repeating the discovery of South Korean researchers. In particular, a group of scientists from the National Physical Laboratory of India in New Delhi and a group from Beihang University in Beijing tried to do this. Both of them synthesized LK-99, but found no signs of superconductivity. The third group, from Southeast University in Nanjing, did not find the Meissner effect (levitation in a magnetic field) in the material, but declared zero resistance of the material to current at a temperature of -163 ° C. This is far from room temperature, but definitely a high-temperature superconductor, and even at ordinary pressure.
A reservation should be made that scientists cannot yet say with certainty that they synthesized the same material as the Koreans. X-ray diffraction was used to analyze the electronic structure of the samples. A team from the National Physical Laboratory of India in New Delhi admitted that the structure of their sample is slightly different from that presented by scientists from South Korea in their work. According to Robert Palgrave, a chemist at University College London, not only the crystal structure of the material differs from the original in the Indian team, but also in the Chinese team, and both of them are completely different. Therefore, it is too early to talk about repeating the experience of Korean scientists.
The crystal structure of the third sample, which was synthesized by a group from Nanjing Southeast University, is more similar to the structure of the original LK-99. And this sample allegedly showed the properties of a high-temperature superconductor, but several scientists pointed out that the resistance measurement was carried out with insufficient sensitivity, in their opinion, and the claim of superconductivity at a temperature of -163 ° C may be a mistake.
The first theoretical studies of LK-99 showed that the material could have interesting properties, including superconductivity. Density functional theory was used for computer analysis of the crystal and electronic structure of LK-99. The first such analysis was made by Sinéad Griffin, a specialist from the Lawrence Berkeley National Laboratory. She found that LK-99 has what are called flat-band zones, where the electrons slow down dramatically. A similar property is associated with the so-called flat-gap Dirac superconductivity. In any case, the detection of “flat zones” means that the material has unusual properties.
Later, Ms. Griffin publicly announced that in no way did she mean that her research proved LK-99 to be superconductive. In fact, scientists still do not have an unambiguous idea of what kind of structure the LK-99 material has. This does not allow a full-fledged analysis of its properties and a confident conclusion about the presence or absence of superconducting phenomena under room conditions. Uncertainty gives birth to hope, but irreproducibility will bury it.
We add that on the English page of the material LK-99 on Wikipedia, a selection of scientific papers on the study of the properties of LK-99 is being carried out. There are now fewer than two dozen studies, but the number continues to grow.
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