The worldwide scientific community is still working around the clock to verify claims of a new superconductor that might yet revolutionize human civilization. Now, we have two pretty convincing videos showing the substance floating in the air. Scientists with the Huazhong University of Science and Technology claim to have replicated LK-99's levitation abilities at room temperature, which they showcased in a video uploaded to Bilibili. And Zhang Chiang, from Wuhan University also in China, has uploaded a new video as of Saturday.
This is an encouraging sign: one of superconductivity's hallmarks, magnetism due to the Meissner effect, seems to be a replicable feature of the copper-lead-apatite compound. If only it were "that easy" to confirm (and understand) the material's zero electric resistance capability and how it manifests.
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The first video below comes from the scientists at the Huazhong University of Science and Technology and, though it's hard to see, there's a small black substance that's allegedly LK-99.
The second video, uploaded to Billibilli by Zhang Chiang, an assistant engineer and doctoral student at the Department of Metallurgical Engineering and Materials of Wuhan University of Science and Technology, showcases what’s claimed to be an LK-99 flake showcasing one crucial aspect of a superconductor’s levitation: flux pinning.
Huazhong University Video
Wuhan University Video
Flux Pinning
The Wuhan University video showcases an LK-99 flake levitating above a powerful magnet. But levitation itself isn’t a sure-sign of a superconductor: most metallic elements showcase diamagnetism by themselves. What differentiates a superconductor’s levitation is that it exhibits flux pinning - an emergent levitation capability that occurs as the pre-existing magnetic field (from the lower magnet) interacts with the superconductor.
The way to differentiate between diamagnetic and flux-pin levitation is that in “normal” levitation, the floating object can be disturbed by outside forces, including gravity - this leads to a floating rock that just can’t seem to stand still, as it glides, balances and wobbles above an ever-changing tug-of-war between it, the magnetic field, and external forces (such as a gust of air, for instance).
Flux pinning, however, pins the magnetic field lines within the superconductor itself. Type-II superconductors (such as LK-99 appears to be) feature internal magnetic vortices; flux pinning happens when the bottom magnet’s own magnetic field (which is actually quantized, that is, discretely composed of impossibly thin action lines, and not a formless cloud) interacts with these magnetic vortices and pinning centers are created.
As the word implies, these centers “pin” the interaction between forces, locking the levitating superconductor in place. In the Wuhan University video, this is seen as the LK-99 flake stays pretty much locked in position above the magnet, despite being poked with the external, probing force of a simple pen
Where LK-99 Tests Stand
The clear-cut update is this: despite the fact the researchers could replicate LK-99's levitation at room temperature, there's still no successful replication of the announced room-temperature LK-99 superconductivity. For that to happen, both the Meissner-effect magnetic field and zero electric resistance are required from the same sample. And while scientists have previously shown that LK-99 does have zero resistivity at -163C, they haven't yet proven it has those properties at room temperature.
So what we're left with (still) is several failed or partially failed replications - and a whole world of additional knowledge on LK-99. The Wikipedia live tracker is one of the best places for anyone looking for up-to-date information on the (public) replication processes currently underway.
The replication difficulties and the nebulous history around superconductors (which have seen several similar room-temperature superconductor claims announced, published, and retracted) combine into a visible, waving, giant red flag. So remember to remove your rose-colored glasses. LK-99 is a fickle thing, and the ground it's standing on is filled with question-shaped potholes.
As our understanding of LK-99 improves, the fuzzy road ahead become slightly clearer. Unfortunately, it seems that the material's characteristics themselves may both be its boon and its blight. That's not to mention the fact that the original scientists did a shoddy job of documenting how they created the material, leaving scientists to patch together samples with a somewhat incomplete cookbook.
As we've explored before, LK-99 is a compound made from reacting lead sulfate with a copper-phosphorous compound. The process through which this compound becomes LK-99 requires that the materials be baked at high temperatures for around 24 hours in a vacuum. This is slightly easier to achieve than it sounds, as several Twitter/X posts and videos of people "owning their own LK-99" will show you (there's also the eternal memory of a Russian soil scientist and her kitchen counter as the first claimed independent synthetization of LK-99).
And adding great to good, the materials aren't even expensive to procure — the materials are all relatively cheap and abundant. But the biggest problem with LK-99 doesn't seem to involve its synthetization; the problem is the lack of control over the chemistry and quantum processes that occur during the fabrication process itself.
Crystals, it turns out, are fickle things. And the way LK-99 seemingly becomes a superconductor has to do with how many lead particles are replaced by copper. As it stands, it seems that the more copper that replaces lead in the final mixture, the purer the resulting compound is (which translates into it showcasing both the emergent levitation courtesy of the Meissner and zero resistance to electrical conductivity).
But that is both the solution and the problem; for now, there's no way for researchers to know what the synthetization process will actually do at an atomic level. So the scenario we're arriving at is that sometimes, there may simply not be enough superconducting elements in a given LK-99 batch for it to showcase any of the superconductive properties we're all hoping it does. It's actually in the formula: the "x" values in Pb10-xCux(PO4)6O, as it's represented in chemistry parlance, mean that it's uncertain just how many of the 10 base lead atoms are replaced with copper atoms. But it seems that the higher the number, the better.
To complicate things even further, however, it's not just a case of having as many copper atoms replace lead as possible; the places where these substitutions occur in the crystal also matter. It seems that some locations are better for unlocking LK-99's superconducting capabilities than others, and for now, once again, we have no way to "pick and choose" what happens during the synthetization process.
Adding insult to injury, the same LK-99 batch can have different ratios of copper atoms replacing lead across its volume. Some will be high, which is good for levitation and bringing a twinkle of excitement to our eyes; some will be low, resulting in a mostly inert compound that would be better used as a doorstop.
And that's saying nothing about how even the most random and seemingly insignificant variances in any of the synthetization steps can introduce unknown variables into replication attempts themselves — especially when researchers are following already badly-documented processes.
Cue the number of failed replication attempts, which, if all this pans out, is likely to keep increasing until it comes to a point where we can design a new synthetization process that improves yield. With all these moving parts, however, it's no wonder we're still walking across a dark room.
It’s still likely that the LK-99 saga will end in disappointment, despite all the lessons and science data being collected and worked on as a result of this. Perhaps it’ll truly happen as some have said (and we ourselves did), in that this discovery will follow the path of cold-fusion. Even if it does, all lessons learned here will inform our future - and the upside is simply too great for us not to try.
Update (Aug 5th): We've added coverage of the second video from Wuhan University.
