Chinese team resurfaces!Room temperature superconductivity is really here
Yesterday, Hao Wu, a postdoctoral fellow, and Li Yang, a doctoral student at the School of Materials of Huazhong University of Science and Technology (HUST), successfully synthesized for the first time the first verified LK-99 crystals that can be magnetically levitated under the guidance of Prof. Chang Haixin.
Through this video we can see that LK-99 is antimagnetic, "indicating that the Korean paper really did not lie."
However, successfully reproducing magnetic levitation only proves that LK-99 is antimagnetic - i.e., that there is a repulsive force with magnets - and does not prove that it has the room-temperature superconducting characteristics claimed by the Korean team. The so-called complete antimagnetism is only a necessary, not sufficient, condition for a superconductor.
This is not at all reflected in the video.
Of course, due to the purity of the sample and the way it was observed, it is not possible to conclude for the moment that LK-99 is not fully antimagnetic: to verify that LK-99 is a room-temperature superconductor, it is crucial to measure whether the sample exhibits zero resistance.
Unfortunately, the sample conditions limit the use of samples that reproduce magnetic levitation for resistance measurements. The Huako lab has also indicated that it has been preparing a new batch of samples in the hope of further measuring the electrical resistance characteristics of LK-99.
Not only Huaxue team, Zhihu respondent "Semiconductor and Physics" also successfully reproduced the magnetic levitation of LK-99 samples in early August. The video he posted at 20:19 is similar to HUST's results, with a very small sample size and a magnet placed underneath it, and one end of the sample lifted.
Since the South Korean team published a paper on arXiv claiming to have discovered the atmospheric pressure room temperature superconductor LK-99, there seems to have been a worldwide frenzy to prepare the material and reproduce the experiment.
Only a few days after the Korean team's paper appeared on the 26th, several sensational events have already been exposed.
At this moment, perhaps we are really standing in front of an unprecedented singularity.
Prior to this, there have been researchers from the National Physical Laboratory of India, Beijing University of Aeronautics and Astronautics and the Shenyang National Laboratory for Materials Science of the Chinese Academy of Sciences have published papers on arXiv claiming to have successfully prepared the LK-99 material and provided X-ray diffractometer analysis results to prove it, but none of them observed the samples to have magnetic levitation and zero resistance.
The Indian team published the paper on arXiv and said, "At present, the results we have obtained on the LK-99 samples synthesized at 925∘C do not demonstrate bulk superconductivity at room temperature. However, further studies on different heat treatments are still in progress."
The Beihang team's paper, published on arXiv, states that "no repulsive force is generated and no magnetic levitation is observed when pressed Pb10-xCux(PO4)6O spheres are placed on top of a commercial Nd2Fe14B magnet at room temperature. These results suggest that the claim of the presence of room-temperature superconductors in modified apatite may need to be reexamined more carefully, especially with respect to electrical transport properties."
Published by the Chinese Academy of Sciences team, the team found that of the doping elements considered (nickel, copper, zinc, silver, and gold), both nickel and zinc doping resulted in gap opening, while gold exhibited doping effects more similar to copper than silver. And, "Our work lays the foundation for future studies of the role of LK-99's unique electronic structure in superconductivity."
Almost at the same time (July 31, 17:58), researchers at the U.S. National Laboratory submitted an arXiv paper with theoretical results showing that it can be confirmed that LK-99 possesses the Fermi energy level flat-band feature of high-temperature superconductors. Sinéad Griffin, a researcher at Lawrence Berkeley National Laboratory, performed density-functional theory calculations on modified lead apatite using U.S. Department of Energy arithmetic and found the presence of a flat band that can span the Fermi energy level, a structure that is also found in many known high-temperature superconductors, and thus the possible existence of superconductivity in LK-99.
Calculations of the energy band structure of spin-polarized electrons in a smaller energy range near the Fermi level show isolated two-energy band Cu-d manifolds. The Fermi level is set to 0 eV and is marked with a dashed line.
As the enthusiasm for this experiment has grown, some users have compiled a list of "competitions" around the world.
Perhaps, with the combined efforts of researchers from all over the world, we will be able to verify whether mankind will be able to take the holy grail of room-temperature superconductivity and enter a whole new era this time.
Today, research related to room-temperature superconductivity has turned out to be an instantaneous process.
A preprint published last week makes the extraordinary claim of a superconducting material (dubbed LK-99) with a temperature well above room temperature at atmospheric pressure. This is one of the hottest targets in the field of materials science and condensed matter physics, and until now, such materials have only appeared in (countless) science fiction novels.
On August 1, the academic journal Science also published an overnight review stating, "Extraordinary claims require extraordinary proofs, and such things usually fail because they are difficult to replicate. However, the experimental preparation of LK-99 was not at all complicated, nor did it use any particularly exotic materials or equipment, so it is to be expected that many laboratories will immediately try to replicate it. Of course, the problem is always complex: even the original authors have said that their samples were polycrystalline and heterogeneous, and there is no expectation that the reported preparation method is optimal. (Whether the authors have a better preparation method yet to be published is still an open question!) . This means that the replication process may not be smooth sailing, but it also means that there will be a lot of people trying, thus increasing the chances of success, even if there are variables that we are not yet aware of. I think that even the variables we know about (purity of starting material, presence of oxygen, particle size, heating and cooling rates, size/shape of container) are enough to create a large number of variables."
"Another complicating factor is the apparent infighting between the authors of the preprints. The two manuscripts appeared in close proximity, one with three authors and one with six. As far as I know (subject to change!) , there are reports that the three-author preprint may be withdrawn, supposedly because one of the authors did not consult several other authors when submitting the preprint, while the six-author preprint is currently being prepared for submission to a peer-reviewed journal (the preprint itself has been revised). It may be some time before we learn what really happened behind the scenes."
The original article also commented scientifically and objectively on the reproduced video from Huazhong University of Science and Technology. And it said, "At least, one video shows that the LK-99 sample is suspended above the magnet due to the Meissner effect and has a different orientation relative to the magnet itself. This is important because paramagnetic materials (only!) can levitate in strong enough magnetic fields, but they can return to a specific orientation like a compass needle."
"Superconductors are 'perfect diamagnets' and can exclude all magnetic fields, which is a big difference. The 'Meissner effect' that you often hear about is when a material first becomes a superconductor at the right temperature, it releases whatever magnetic field is penetrating it at the time. IMO, we have to take this video at face value based on what the person who made/published it says, and there are other possible explanations that don't involve room temperature superconductivity. I would be very happy if this was a true replication."
"Although I usually prefer experimental results to theory, I am very interested in two other new pre-publication papers. One is from a team at Shenyang National Laboratory for Materials Science, and the other is from Sinéad Griffin at Lawrence Berkeley U. Both papers take the reported LK-99 X-ray structural data as a starting point and study its predicted behavior through density-functional theory (DFT) calculations. They came to very similar conclusions: it works. This is quite important because it could mean that we don't need to assume entirely new physics to explain something like LK-99."
"Griffin's paper states directly that the simulation results apply to the substitution of copper atoms into the lead (1) position in the apatite lead structure, as reported in the original preprint, but her calculations indicate that substitution into another position, lead (2), appears to be energetically more favorable; this suggests that it may be energetically difficult to obtain copper substitution robustly in the lead (1) position; this suggests that there may be difficulties. Thus, this would be a source of variability for reproducing LK-99, or at least for obtaining particularly clean bulk samples."
"Meanwhile, the Shenyang group came to very similar conclusions (they used the same DFT software package as Griffin). The starting apatite lead is a very good insulator, but the structural changes after the addition of the copper atoms both match the experimental data in the Korean preprint and lead to a dramatic transition to the metallic state. They found a half-filled flat band and a fully occupied flat band near the Fermi level, and agreed that these were crucial to the superconductivity reported in the study. They also predicted that replacing gold atoms into the lead(1) sites might produce a material with very similar properties, which would be a very interesting idea worth experimenting with."
An illustration of the Shenyang group's experiment.The energy band structure of LK-99 near the Fermi energy level is characterized by a half-filled flat band and a fully occupied flat band. The two flat bands arise both from the 2p orbitals of the 1/4-occupied oxygen atoms and from the hybridization of the 3d orbitals of Cu with the 2p orbitals of its nearest neighboring oxygen atoms.
"They do not, however, delve into the possible low-energy substitution at the Pb(2) site, but the above warning about fragile electronic properties may also explain some of the variation in the material's behavior (although this must be balanced against the initial report of superconductivity beyond the temperature of boiling water!) ."
This also highlights a point that occurred to everyone reading the original preprint: it seems likely that superconductivity would occur along only one crystal axis if a good single crystal of LK-99 could be grown: in short, if a wire is hooked on two specific opposite faces of the crystal, superconductivity will be seen, while hooking it on the other faces will not! It is well known that crystal boundaries are an important factor in the efficiency of existing superconducting materials, which means that the polycrystalline samples of LK-99 will be very unfavorable for demonstrating powerful effects.
The article also ends with the authors stating that they will be cautiously optimistic. "The Shenyang and Lawrence Berkeley calculations are very positive developments that take this problem completely out of the 'we can't explain it' category of cold fusion. I await more replication data, not just social media video support."
"This is by far the most plausible room temperature-pressure superconductivity phenomenon in the world, and the coming days and weeks will be very interesting."
The phenomenon of superconductivity was first discovered in 1911 by a team of researchers at Leiden University in the Netherlands by H.K. Onnes - the sudden disappearance of the resistance of metallic mercury to zero below 4.2 K, which Onnes named "superconductivity", meaning Superconductivity", meaning "super conductivity". Subsequently, more than a hundred years, all kinds of superconducting materials have been discovered, and there are now thousands of known superconducting materials, covering monolithic metals, alloys, intermetallic compounds, transition-metal sulfur/phosphorus compounds, and even organic compounds.
Superconducting materials are of immense application value in almost all electrical and magnetic related fields due to their special physical properties such as absolute zero resistance and perfect antimagnetic properties.
In the last decade, high-pressure compression techniques have dominated the search for high-temperature superconductivity. Leading the way was the "chemical pre-compression" of hydrogen-dominated alloys, which demonstrated the critical superconducting transition temperatures (Tc) of the rare-earth hydrides LaH10 and YH9 at megapascals close to the freezing point of water.
After 37 years of research, copper oxide and nickel oxide superconductors are the unconventional superconducting materials known to have superconducting transition temperatures that break through the temperature region of liquid nitrogen.
Unlike high-temperature superconductivity, room-temperature superconductivity is important because it has the potential to revolutionize multiple aspects of science and technology. One of the most significant advantages of room-temperature superconductors is their unprecedented energy efficiency. Conventional superconductors require extremely low temperatures to function, which makes them limited and energy-intensive for practical applications. However, with room-temperature superconductors, the resistance of the transmission and distribution system is virtually zero, resulting in minimal energy loss.
In addition, the advent of room-temperature superconductivity could pave the way for groundbreaking advances in transportation, such as high-speed trains that can travel without using large amounts of energy. In addition, superconducting materials could be used in energy storage devices, providing efficient and compact solutions for grid-level energy storage and portable electronics.
Quantum computing will be a direct beneficiary of this work, and with room-temperature superconductivity, quantum computing will become more practical and accessible. Most quantum computers need to operate at ultra-low temperatures close to absolute zero to minimize noise. This extreme cooling requirement is not only technically challenging and costly, but also limits the scalability of quantum computing systems. Room-temperature superconductors, with their ability to conduct electricity without resistance at ambient temperatures, can provide a stable, controlled environment for quantum bits without the need for complex cooling systems.
Reference Links:
[1] https://www.zhihu.com/question/613850973/answer/3136586869
[2]https://view.inews.qq.com/a/20230802A003JY00?no-redirect=1
[3]https://arxiv.org/abs/2307.16802
[4]https://arxiv.org/abs/2307.16402
[5]https://arxiv.org/abs/2307.16040
[6]https://mp.weixin.qq.com/s/2wQbmRcAcxdlpde8p3LSjw
[7]https://www.science.org/content/blog-post/room-temperature-superconductor-new-developments
