[pistachiopro]

You can publish an article with a title like this and probably not end up embarrassed. Room temperature and pressure super conductors seem hard enough to find that chances are any given paper claiming to have found one will end up with a more mundane explanation. And I do think the information about the phase change of Cu2S is highly relevant, as it points at a way the original researches my have fooled themselves.

The dismissal of the partial levitation as ferromagnetism, on the other hand, doesn't strike me as especially robust. Ferromagnetism explains the partial levitation of tiny fragments of material generated by people trying to reproduce LK-99. Very light and thin pieces of ferromagnetic material will align themselves with a magnetic field. For example, Andrew McCalip (who streamed himself attempting to reproduce the material in his rocket startup's lab) generated a partially levitating fragment and sent it into USC, where they determined it was ferromagnetic. But bulk pieces of ferromagnetic material will just stick to magnets (or if they are magnetized, they will stick to one side and be unstably repelled from the other).

Ferromagnetism doesn't explain the levitation demonstrated in the videos put out by the original researches, though. Barring fraud, the most likely explanation for that kind of levitation is diamagnetism. The article mentions Derrick van Gennep recreating the partial levitation video with a chunk of pyrolytic graphite (one of the most diamagnetic materials we know of, other than superconductors), supergluing iron filings to a corner of it to anchor it to the magnet. The levitation in that video comes from diamagnetism, not ferromagnetism. LK-99 is primarily made of lead, not graphite, which is 5-10 times denser, so the diamagnetic effect must be at least that much stronger than pure pyrolytic graphite. The thing is, as the rest of the article points out, the supposed main constituents of LK-99 have now been extensively studied, and none of them appear to be especially diamagnetic, so something in those samples the original team recorded must be extremely diamagnetic to make up for it!

[floxy]

>so something in those samples the original team recorded must be extremely diamagnetic to make up for it!

I wonder what would have happened if they would have pushed a paper out talking about anomalously high diamagnetism and skipped any mentions of superconducting. And let people speculate if it is a superconductor. I suppose we wouldn't be talking about it. But I hope that we see some group try to replicate the diamagnetic material properties.