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Semiconducting Transport in LK99 reproduction attempt

arxiv.org

31–40 of 269 posts

Re: Semiconducting Transport in LK99 reproduction attempt

#31
post #7

> In addition, when a pressed Pb10-xCux(PO4)6O pellet is located on top of a commercial Nd2Fe14B magnet at room temperature, no repulsion could be felt and no magnetic levitation was observed either. Unless we assume the original paper's authors were straight up lying, it sounds like this paper's author didn't end up with exactly the same material?

They mention the possibility of a mistake when measuring resistivity, which has already been discussed.

But yeah, the partial levitation is not a mistake. Their abstract suggests LK-99 is a "highly insulating diamagnet", but they are not even able to "detect any reliable diamagnetic signal" with their instruments.

I'd rank the possibilities as: fraud, a different material, or some comical series of bizarre mistakes and contamination from the original team.

Re: Semiconducting Transport in LK99 reproduction attempt

#32
Research out of Berkeley, 1 Aug 2023: theoretical analysis suggests high-Tc superconductors from apatite possible, points to synthesis challenges.

> Finally, the calculations presented here suggest that Cu substitution on the appropriate (Pb(1)) site displays many key characteristics for high-TC superconductivity, namely a particularly flat isolated d-manifold, and the potential presence of fluctuating magnetism, charge and phonons. However, substitution on the other Pb(2) does not appear to have such sought-after properties, despite being the lower-energy substitution site. This result hints to the synthesis challenge in obtaining Cu substituted on the appropriate site for obtaining a bulk superconducting sample.

https://arxiv.org/abs/2307.16892

Edit: Layperson summary from https://twitter.com/Andercot/status/1686215574177841152. It's crazy for the sim to not only be favorable towards SC, but also showing results that align with what the researchers proposed and what the replicators are experiencing (difficulty in synthesis).

> The simulations modeled what the original Korean authors proposed was happening to their material - where copper atoms were percolating into a crystal structure and replacing lead atoms, causing the crystal to strain slightly and contract by 0.5%. This unique structure was proposed to allow this amazing property.

> Lastly, these interesting conduction pathways only form when the copper atom percolates into the less likely location in the crystal lattice, or the 'higher energy' binding site. This means the material would be difficult to synthesize since only a small fraction of crystal gets its copper in just the right location.

Re: Semiconducting Transport in LK99 reproduction attempt

#33
post #17

> In addition, when a pressed Pb10-xCux(PO4)6O pellet is located on top of a commercial Nd2Fe14B magnet at room temperature, no repulsion could be felt and no magnetic levitation was observed either. So what about the video[1] that shows magnetic levitation occurring? Since the linked article was unable to reproduce this effect, it seems there are two possibilities: 1. The video is fake (which is really, really hard…

Apparently a new paper is supposed to come out from the original authors about the production method [0]. So it really is unclear whether everybody generates the same material. It's a shame that these papers were published before they were polished by the authors. [0] https://forums.spacebattles.com/threads/claims-of-room-tempe...

Seems the fastest way to clear this up would just be for the original team to send a sample to some other scientists for testing. That would solve any issues regarding other teams reproducing the material incorrectly, and at a first pass, what everyone cares about is whether its a superconductor at room temp, not how to make it.

Re: Semiconducting Transport in LK99 reproduction attempt

#34
post #26

Earlier quoted context omitted.

> It's a shame that these papers were published before they were polished by the authors. Indeed. It's also a shame that they chose to use language like: "We believe that our new development will be a brand-new historical event that opens a new era for humankind." When you make grandiose boasts like these, you better be fucking certain you are correct.

You'd think they'd find a new word

"superpressreleasing"

Re: Semiconducting Transport in LK99 reproduction attempt

#35
post #31
post #7

> In addition, when a pressed Pb10-xCux(PO4)6O pellet is located on top of a commercial Nd2Fe14B magnet at room temperature, no repulsion could be felt and no magnetic levitation was observed either. Unless we assume the original paper's authors were straight up lying, it sounds like this paper's author didn't end up with exactly the same material?

They mention the possibility of a mistake when measuring resistivity, which has already been discussed. But yeah, the partial levitation is not a mistake. Their abstract suggests LK-99 is a "highly insulating diamagnet", but they are not even able to "detect any reliable diamagnetic signal" with their instruments. I'd rank the possibilities as: fraud, a different material, or some comical series of bizarre mistakes a…

While fraud is always possible, so far I'm not getting fraud vibes. I'm really rooting for an eventual outcome somewhere between: "These guys are an experimental mess but damn it seems to kind of work" and "It's not a room temp superconductor but it is something new, interesting and maybe even useful."

Re: Semiconducting Transport in LK99 reproduction attempt

#36

Research out of Berkeley, 1 Aug 2023: theoretical analysis suggests high-Tc superconductors from apatite possible, points to synthesis challenges. > Finally, the calculations presented here suggest that Cu substitution on the appropriate (Pb(1)) site displays many key characteristics for high-TC superconductivity, namely a particularly flat isolated d-manifold, and the potential presence of fluctuating magnetism, cha…

Some days I wish I could just run DFT on everything and have it spit out the ones with "interesting" results and then patent those. Unfortunately, this is not feasible (computationally) nor likely to produce very many true positives.

I wonder if you could troll theorists into doing simulations of just about any substance by publishing convincing-looking papers in arxiv. Scratch that: we know it's possible.

Re: Semiconducting Transport in LK99 reproduction attempt

#37
post #8

Doesn't it seem like there should be some sort of annealing process required? this material being essentially a powder smashed into a tablet form seems like it would likely be a very poor conductor unless the superconducting properties not only existed in each of the granules of the powder, but also can easily transition between each of the boundaries. So wouldn't you want the final thing to be closer to like a ceram…

Unequivocally yes… which is why I wasn’t surprised when the first publicised reproduction involved a tiny grain, why the big pressed pellets seem to be staying put, why people are suggesting breaking the samples up, and why the original pictures/video showing the levitation that kicked all this off, is an oddly shaped sample that sort of looks like it flaked off a larger piece.

Smash the samples… see if any of the grains float… (it’s becoming a bit of a refrain on Twitter whenever a big chunky pressed pellet sample is published as a failed replication) … it won’t be hard to improve the process and try and get larger contiguous samples that show the effect once we know for sure that it’s actually happening even if it’s happening in smaller more obviously superconducting samples, be it the size of a sand grain or a grain of rice, as long as it’s clearly a room temperature superconductor… once we have more samples… the analysis experts can get stuck in, there’s a global army of analytical experts… crystallographers, spectrographers, and all the sub disciplines of analytical chemistry… with clearly superconducting samples these people can swing into action and work out what the magic is and what we have to do to make more and bigger floating rocks.

Re: Semiconducting Transport in LK99 reproduction attempt

#38
post #4
post #2

The biggest question in this whole thing was, why not bring a sample to another lab for verification? Well, now we’re starting to get some reproduction attempt results anyways.

because they just got a few mm^3, not done experimenting with it, and was not ready to publish?

> because they just got a few mm^3

But why? The base materials are cheap and easily available, and the synthesis process seems rather straightforward. Why don't they have kilograms of this stuff by now?

Re: Semiconducting Transport in LK99 reproduction attempt

#39
post #36

Research out of Berkeley, 1 Aug 2023: theoretical analysis suggests high-Tc superconductors from apatite possible, points to synthesis challenges. > Finally, the calculations presented here suggest that Cu substitution on the appropriate (Pb(1)) site displays many key characteristics for high-TC superconductivity, namely a particularly flat isolated d-manifold, and the potential presence of fluctuating magnetism, cha…

Some days I wish I could just run DFT on everything and have it spit out the ones with "interesting" results and then patent those. Unfortunately, this is not feasible (computationally) nor likely to produce very many true positives. I wonder if you could troll theorists into doing simulations of just about any substance by publishing convincing-looking papers in arxiv. Scratch that: we know it's possible.

You think it's over? Or are we back?

Re: Semiconducting Transport in LK99 reproduction attempt

#40
post #17

> In addition, when a pressed Pb10-xCux(PO4)6O pellet is located on top of a commercial Nd2Fe14B magnet at room temperature, no repulsion could be felt and no magnetic levitation was observed either. So what about the video[1] that shows magnetic levitation occurring? Since the linked article was unable to reproduce this effect, it seems there are two possibilities: 1. The video is fake (which is really, really hard…

From what I have gathered reading things online, there is some theorizing that given a "perfect" baking process there is something probabilistic going on that means your batch is never 100%. disclaimer not a physicist or chemist

I'm not a material scientist, but I've spoken with folks who do advanced vapor deposition and thin-film synthesis for high-temperature superconductors (the ones that work at liquid-nitrogen temperature).

It's basically witchcraft-adjacent, with so many variables that getting everything right is an art. That's why we're only now getting practical high-TC superconducting tape, even though the original materials were discovered in 80-s.

The best way right now would be for the Korean team to send their sample to a reputable lab for testing. Once its properties are verified, labs can start deconstructing the process.

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