Superconductors are one of the most significant research areas in solid-state physics. However, there are some obstacles to the widespread use of them, which can be used in important innovations for our lives in every field that uses electrical energy, from transportation to medicine. Superconductors, which gained great interest in the scientific world due to their potential, also started to attract peoples’ attention on social media with an article published on July 22.
Under normal conditions, every conducting material has an electrical resistance, so no material conducts electricity with full efficiency. For better understanding, here is an example from everyday life: you may have noticed that technological devices heat up during your usage, this is due to the resistance that electrons encounter as they flow through the wires. This means that some of the initial total electrical energy has been converted into heat energy. Superconductivity is when there is zero electrical resistance of certain materials when cooled to a temperature below their critical temperature (below 20K for most materials). In this case, the initial electrical energy can be transmitted with full efficiency.
In addition to the disappearance of electrical resistance, the Meissner effect is also one of the uniquenesses observed in superconductivity. According to the Meissner effect, sufficiently weak external magnetic fields do not penetrate the superconductor but remain on the surface of the material. This is called the expulsion of the magnetic field. It is not perfectly demonstrated in all types of superconductors, with Type II superconductors being able to tolerate the penetration of the magnetic field to a certain point.
In addition, the Meissner effect of superconductors leads them to be described as highly diamagnetic. We know diamagnetic materials are repelled by magnets. In this case, every superconductor is diamagnetic, but not every diamagnetic is a superconductor. On the other hand, ferromagnetic materials (except for a special class of materials) are generally not considered to be superconductors because ferromagnetic materials show great attraction to magnets, and superconductors are considered to lose their properties at high magnetic fields. Therefore, the critical temperature and magnetic field are important for the maintenance and formation of superconductivity.
The first superconductor, discovered in 1911 by Heike Kamerlingh Onnes and her team, was mercury and had to be cooled to -269 Celsius to become a superconductor. By 1986, scientists had discovered a new class of copper-oxide material that could superconduct at higher temperatures than the metal superconductors known to date. The discovery of high-temperature superconductors was a hopeful step toward the discovery of room-temperature superconductors.
Although superconductors are now used in Maglev trains, MRI machines, and particle accelerators, they are not widely used in everyday life because the material needs to be cooled to very low temperatures. A superconducting material doesn't have to be a very good conductor, and sometimes even relatively poor conductors can be better superconductors, but the cooling process makes these technologies expensive and impractical. Unlike other superconductors, high-temperature superconductors can be cooled with liquid nitrogen instead of liquid helium, which is cheaper, but even this is not enough to reduce costs drastically and expand use.
Room-temperature superconducting materials could be used to conduct electricity in widely used electrical systems at full efficiency without the need for cooling the material. The widespread use of superconductivity in everyday life can reduce the environmental impact of power plants, increase energy efficiency, and contribute to the production of technological devices that can do more with less material. In this context, many studies are being conducted on smaller but more powerful electric motors, supercomputers, or the use of superconducting wires in telecommunications.
We understand the importance of room-temperature superconductors, but is room-temperature superconductivity a realistic aspiration, moreover, is LK-99 really a material with this property? First of all, based on the studies that have been published so far, we have two options for a definitive answer to this question: first, to synthesize or discover a room-temperature superconducting material, and second, to provide an overarching scientific explanation for the behavior of superconductors.
The BCS (Bardeen-Cooper-Schrieffer) theory, one of the most respected theories of electron behavior in superconductors, cannot explain the behavior of all superconductors. Based on this situation, we can say that finding the reasons for the behavior of superconductors and commenting on the substances that can be superconductors at room temperature requires long-term scientific research processes. But what about synthesizing such a substance?
Let's skip the previous claims of synthesizing a superconducting substance at room temperature and examine what has been said about LK-99. In articles published on July 22 [1] and August 11 [2], the scientists who synthesized LK-99 claim the following: LK-99 is a superconductor with a critical temperature equal to or greater than 400 Kelvin, exhibits the Meissner effect, and can superconduct at room temperature because its superconductivity is due to a volumetric distortion in its structure, not external factors. This claim by Korean scientists had a huge impact on social media and at first, everyone was excited, thinking that they were witnessing a revolutionary discovery. However, the reaction from the scientific community did not match the excitement, and was skeptical.
After weeks of replicating and publishing papers, many opinions that LK-99 is not a superconductor have been formed. These opinions also offer plausible explanations for the behavior of the material that the Korean scientists cited as evidence. Here are some of these arguments:
When Derrick VanGennep, a former condensed matter researcher at Harvard University who was intrigued by LK-99, watched the video presented as the biggest piece of evidence, he thought the behavior was more like ferromagnetic materials than superconductors. In the video, LK-99 is levitating on a magnetic material, but it is in equilibrium with part of it sticking to the material. In contrast, superconductors levitating on magnets are known to be able to be rotated or even held upside down. So, he built a pellet of compressed graphite shavings with iron filings glued on top. A video made by VanGennep shows his disk made of non-superconducting, ferromagnetic materials imitating the behavior of LK-99. The Peking University team also attributes this quasi-levitation to ferromagnetism, but they cannot find an explanation for the sharp drop in resistance.
An insightful interpretation of the drop in resistance comes from chemist Prashant Jain of the University of Illinois. Jain noticed that when this copper-doped sulfur phosphate mixture was synthesized, it produced 17 parts of copper and 5 parts of sulfur for each part. He says there is something overlooked here, the residual Cu2S left over from the synthesis. This residue leads to impurities, and it is a known fact that CU2S experiences a severe resistance drop at temperatures below 104 degrees Celsius. This is the same temperature at which the critical resistance drop the Korean team is talking about.
The examples above are just a few of the arguments compiled by Nature author Dan Garisto, but there are many more questions, criticisms, and posts about the real properties of matter by scientists and people interested in science on social media networks. As a principle of science, the burden of proof lies with the claimant. So, at this point, we cannot say that LK-99 is a superconductor at room temperature, but we cannot accept the opposite as a fact either, because no matter how close the replicas are to the truth, we do not have enough information to achieve the same synthesis. When we put it on the scales, as scientists are unanimous in saying, the probability of it not being a superconductor at room temperature weighs heavily. At this point, a new explanation should come from Lee, Kim, or Q-Centre(Quantum Energy Research Center).
Finally, we should mention that many users on social networks made a joking accusation over this material. Some people say that this is a deliberate scam to draw attention to the industry and that such scientific scams have recently become widespread. There is no denying that scientific scams do exist, but it would be paranoid to automatically say that it is a trick of the markets.
I believe that investigating the changes in stock prices following these claims might have led us to find out how this news affected the market. I came across an organization called the American Superconductor Corporation and noticed that there was a significant increase in the stock prices of this organization on August 1-2. Although I cannot reach definite results about other similar companies, I found it possible that investors might have developed an interest in this organization due to this alleged revolutionary invention. The reason I conclude that the organization will not benefit from this superconductor is that I think that such a revolutionary material will probably receive investment from the advanced electronic network of its own country and benefit its own country.
While I'm always happy to see a renewed interest in science, it's better to be careful when making claims about potentially revolutionary innovations. We will carefully follow any announcements from Q-Centre in the future, but for now, it seems that our dreams of an innovation that will profoundly affect our lives have been dashed.
Written by Nehir Türkmen
Edited by Bilge Öztürk & Yağmur Ece Nisanoğlu
Works Cited:
Cho, Adrian. “A spectacular superconductor claim is making news. Here's why experts are doubtful.” Science, 27 July 2023.
“DOE Explains...Superconductivity.” Department of Energy
Garisto, Dan. “LK-99 isn’t a superconductor — how science sleuths solved the mystery.” Nature, 16 August 2023.
Ginsberg, Donald M. “Superconductivity | Physics, Properties, & Applications.” Britannica, 11 August 2023.
“Ferromagnetism & curie temperature | Magnetism & matter | Physics | Khan Academy.” YouTube, 4 May 2021.
Lee, Sukbae, et al. “[2307.12037] Superconductor Pb10-xCux(PO4)6O showing levitation at room temperature and atmospheric pressure and mechanism.” arXiv, 22 July 2023.
Lee, Sukbae, and Ji-Hoon Kim. “[2307.12008] The First Room-Temperature Ambient-Pressure Superconductor.” arXiv, 22 July 2023.
Lowe, Derek. “A Room-Temperature Superconductor? New Developments.” Science, 1 August 2023.
“Making Superconductivity Useful.” DOE Office of Science, 2018.
“Superconductivity.” CERN.
University of Calgary. “Superconductor.” Energy Education.