As I feared, it is no use at all at this stage to claim anything about LK-99 as every synthesized LK-99 seems different each time. We have to have a thorough analysis on the sample directly provided by Lee and Kim.
> We have to have a thorough analysis on the sample directly provided by Lee and Kim.
Even this sample could be marginal, going by the original paper.
But there has been plenty of "locked" levitation and lots of zero conductance failures. I believe LK-99 a finicky topological superconductor thats going to give researchers headaches for years, not something that will suddenly be a bulk superconductor with just the right synthesis in the coming months.
It seems people are throwing around more and more random physics keywords without any type of evidence. What makes LK-99 a topological superconductor? Topological quantum states and the associated Majorana fermions have only been observed in their bound state so far (and only in highly engineered quantum systems), and there's absolutely no indication that they should exist in that material, at least I don't see how you could postulate that by observing levitation or measuring an IV curve in a bulk sample.
Calling it "LK-99" seems to have been a mistake. It gives the impression that the term refers to a well-defined material, perhaps even a mass-produced product like "iPhone 14" or "RTX 4080". This explains all the calls for the original authors to send samples, as if you were ordering from AliExpress.
In reality, what we have is a family of lead-copper-phosphorus-oxygen compounds, each with a different crystal structure, some of which might or might not exhibit interesting properties.
If this hype doesn't fizzle out soon, scientists will probably converge on more neutral, precise terminology to refer to the various configurations in order to avoid talking past one another. Something like β-LK99-Cu-5-7.
Hopefully the controversy doesn't cloud researcher's judgement and cause us to miss out on the technology just because it was way more nuanced than first appeared.
It might also be that everyone loses interest and the original team get the extra time they needed to work in peace and make a comeback.
> Even this sample could be marginal, going by the original paper.
If the sample they claim is superconducting isn't superconducting; why should we assume that this material is a superconductor at all? Because of some vague idea that their prof thought it might be more than 2 decades ago?
The quality and depth of the analysis here far exceeds the work done by the original Korean team. It is very unlikely the Korean team has successfully manufactured the Cu-doped phase given the thermodynamic mountain required to climb, and its clear anybody attempting to replicate their recipe was essentially producing a random assortment of garbage.
The Korean team needs to disclose any alternative formulations or just accept failure and move on.
Original authors have been working on it for 23 years since they first found the material in 1999. They are part of private institution and have no incentive to rush the disclosure so that other labs can catch on their life's work. Authors already have stated they will publish more information next year. It's pretty arrogant to draw premature conclusions on quick analysis and demand the authors to disclose more information right now, when they are clearly not obligated to anything.
The original Korean team paper was supposedly a rushed job because of inside fight at the research center, so it is expected the quality is poor by default. We still have to wait for a more polished proper research paper from the team to judge whether it is legit or not (APL material is their choice of journal I believe). We can speculate whether the Korean team has achieved superconductivity or they are under delusion based on replication papers published on arxiv, but such papers have never come under the scrutiny of peer review process as well. So I would reserve my conclusion about this at this stage. It is just frivolous to say whether LK-99 is superconductor or not for now.
I don't know why so many institutions and scientists are so quick to call it nothing. It feels like hubris to me, the scientists in Korea spent many years on it, if it were so easy to dismiss I don't think that would have continued their research... right?
> The superconducting-like behavior in LK-99 most likely originates from a magnitude reduction in resistivity caused by the first-order structural phase transition of Cu2S
The preprint you are citing is explicitly dismisses the sharp transition seen as being non-superconducting.
Or everyone has to wait for the full paper to be released which supposedly includes some manufacturing steps not included in the leaked paper so that replication can happen properly.
The original samples are now under testing at a national lab in SK.
Well Occam's razor is to rescue. As for now "LK-99 is not superconductor" is the simplest claim consistent with all experimental evidence. That's not awfully specific, but since specifics are not very impactful, people won't rush to clarify it.
If anyone (probably original authors) provide something that contradicts this claim then we'll need to revise it
Honestly I'm excited by that. Seems like a big space opened up for exploration. I think over the next few years there will be several types of this composition with varying electro-magnetic properties.
I disagree. I think that given the multiple failed attempts from numerous top tier labs we should say this isn’t a SC unless L&K share their sample and it proves to be.
* multiple successful attempts of levitation/flux pinning.
The hard part is going to be figuring out how to actually isolate the superconducting effect such that it can be tested. We already know the SC effect isn't uniformly spread throughout the ceramic.
eh, most of the synthesized LK-99 out there by the different teams share enough commonalities and seem very promising from the levitation/flux pinning effects.
A dismissal coached by a theoretical physicist (Bernevig [0], the others appear to be students or postdocs) whose job it is to predict superconductors.
At least two reactions come to mind:
1) If his models could predict useful room temperature superconductors, it seems we would have found one already.
2) If his models don’t agree with LK-99 being a superconductor, and it ends up being one, he probably has a lot of revision to do.
I’m not an expert, but doesn’t it seem likely that finding a room temperature superconductor at this point would involve effects or combinations of effects that we don’t have a good theoretical framework for yet?
That's a pretty condescending take on what's evidently a paintakingly put-together theoretical+experimental study, from one of the best condensed matter groups in the world.
Believe it or not, researchers more than any other people love the possibility of previously-undiscovered exotic phenomena; these guys are not coming into this with the agenda of enforcing orthodoxy and stifling a potential discovery. But materials still ought to be consistent with what we know about the laws of physics, and it's totally valid to check this via theory and experiment.
To use an example from a different domain, finance, it is completely fair to be skeptical of models and assume there's huge things they may miss. In that case, we have seen models predict things like "this scenario should only happen once in a billion years" - and then occur a few times on consecutive trading days. "Don't overtrust the model" is practically an object lesson at this point, assuming the 'model' here is actually a model and not a literal restatement of physical laws.
> assuming the 'model' here is actually a model and not a literal restatement of physical laws.
I'm not sure there is a difference. Imhu, what we call "physical laws" are always models. Like, Newton's theory of gravity, which predicts that gravity is inverse to the square of the distance. Then Einstein came along and made a better model with relativity theory. Which cannot be the end of the story, because it is incompatible with quantum mechanics...
> If his models could predict useful room temperature superconductors, it seems we would have found one already.
This sort of model works like "put these atoms in this configuration, find the favourable energy states, look to see if we see signatures that might indicate superconductivity"
They are not "given the whole infinite number of chemicals and configurations of atoms, tell me which ones are superconducting"
I’m confused how you think it doesn’t follow? Maybe our conception of model is at differing levels?
I’m saying that if their models worked in a predictive way, since they have been established for so long and the value of confirming them is so high, they would have been confirmed by now.
From what I understand of the state of modeling here, it's like verifying primes. It's relatively easy to verify whether a specific number is prime or not, but very difficult to generate a new one. Likewise if you know the specific structure of a material, we can model / characterize it but the search space is so large that it's beyond our capabilities to find new candidates.
> If his models could predict useful room temperature superconductors, it seems we would have found one already.
A model that can check a given solution is not one that can quickly check the entire solution space. For a pure-CS analogy, this is the very definition of P vs NP.
She uploaded her weekly news video yesterday. Seems to remain skeptical but not openly so, simply highlighted that most replication attempts are inconclusive or failed, and commented on some of the new papers (thr DFT theoretical one, 100K SC one...).
"Together, these calculations suggest it is doubtful that Cu enters the structure in meaningful concentrations, despite initial attempts to model LK-99 in this way."
So does this mean all those DFT calculations were useless?
It may mean the structure of LK-99 found by Kim et al is highly metastable. It does not mean the DFT calculations were useless. Also, for clarity, the original DFT calculations by Griffin do not purport to have “verified” superconductivity, but rather just report to have found a band structure (electronic energy levels) which are encouraging.
The DFT calculations were performed on a phase which is not possible to form via the recipe provided by the Korean team, as demonstrated by this latest preprint.
Which raises doubt on what the Korean team actually tested or whether they are withholding alternative recipes.
Think of it in terms of an energy barrier, like someone cycling over Everest. It might be theoretically possible that there's a nice happy superconducting state if you can get things in the right place, but if you've got to cycle over the top of Everest, it might be pretty much impossible to get there.
Reading about this reminds me of carbon nano tubes and graphene: extremely interesting and useful properties but no reliable, reproducible mass manufacturing techniques mean we have no (or only very very limited) real world applications.
The apparent drop in resistivity originally shown by the Koreans can be attributed to the Cu2S phase change. The crystal structure changes with temperature, and that changes its conductivity. The resistivity never becomes zero but drops sharply to near-zero. It's so cleanly explained, I can't believe it's not over so it has to be over.
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Even this sample could be marginal, going by the original paper.
But there has been plenty of "locked" levitation and lots of zero conductance failures. I believe LK-99 a finicky topological superconductor thats going to give researchers headaches for years, not something that will suddenly be a bulk superconductor with just the right synthesis in the coming months.
In reality, what we have is a family of lead-copper-phosphorus-oxygen compounds, each with a different crystal structure, some of which might or might not exhibit interesting properties.
If this hype doesn't fizzle out soon, scientists will probably converge on more neutral, precise terminology to refer to the various configurations in order to avoid talking past one another. Something like β-LK99-Cu-5-7.
Hopefully the controversy doesn't cloud researcher's judgement and cause us to miss out on the technology just because it was way more nuanced than first appeared.
It might also be that everyone loses interest and the original team get the extra time they needed to work in peace and make a comeback.
my favorite xkcd: https://xkcd.com/683/
If the sample they claim is superconducting isn't superconducting; why should we assume that this material is a superconductor at all? Because of some vague idea that their prof thought it might be more than 2 decades ago?
The Korean team needs to disclose any alternative formulations or just accept failure and move on.
https://arxiv.org/abs/2308.04353
I don't know why so many institutions and scientists are so quick to call it nothing. It feels like hubris to me, the scientists in Korea spent many years on it, if it were so easy to dismiss I don't think that would have continued their research... right?
The preprint you are citing is explicitly dismisses the sharp transition seen as being non-superconducting.
The original samples are now under testing at a national lab in SK.
Replication has failed pretty thoroughly.
As everyone seems to keep forgetting the original scientists said that less than 10% of their replication attempts was successful.
We don't have 10 replications total let alone 10 based on their exact process which is unknown to everyone except them at this point.
So not sure on what basis you can claim replication has thoroughly failed.
The hard part is going to be figuring out how to actually isolate the superconducting effect such that it can be tested. We already know the SC effect isn't uniformly spread throughout the ceramic.
At least two reactions come to mind:
1) If his models could predict useful room temperature superconductors, it seems we would have found one already.
2) If his models don’t agree with LK-99 being a superconductor, and it ends up being one, he probably has a lot of revision to do.
I’m not an expert, but doesn’t it seem likely that finding a room temperature superconductor at this point would involve effects or combinations of effects that we don’t have a good theoretical framework for yet?
[0] https://phy.princeton.edu/people/bogdan-bernevig
Believe it or not, researchers more than any other people love the possibility of previously-undiscovered exotic phenomena; these guys are not coming into this with the agenda of enforcing orthodoxy and stifling a potential discovery. But materials still ought to be consistent with what we know about the laws of physics, and it's totally valid to check this via theory and experiment.
I'm not sure there is a difference. Imhu, what we call "physical laws" are always models. Like, Newton's theory of gravity, which predicts that gravity is inverse to the square of the distance. Then Einstein came along and made a better model with relativity theory. Which cannot be the end of the story, because it is incompatible with quantum mechanics...
This sort of model works like "put these atoms in this configuration, find the favourable energy states, look to see if we see signatures that might indicate superconductivity"
They are not "given the whole infinite number of chemicals and configurations of atoms, tell me which ones are superconducting"
How do you arrive at this?
I’m saying that if their models worked in a predictive way, since they have been established for so long and the value of confirming them is so high, they would have been confirmed by now.
> I’m not an expert, but..
No such models exist.
A model that can check a given solution is not one that can quickly check the entire solution space. For a pure-CS analogy, this is the very definition of P vs NP.
Edit: apologies, meant to link to this more recent update (still skeptical): http://backreaction.blogspot.com/2023/08/superconductor-lk99...
So does this mean all those DFT calculations were useless?
Which raises doubt on what the Korean team actually tested or whether they are withholding alternative recipes.
I hope LK99 does not end up in the same place...
Perhaps the original authors didn’t realize that and got over excited… then fell victim to confirmation bias elsewhere…
I still have some hope!
The apparent drop in resistivity originally shown by the Koreans can be attributed to the Cu2S phase change. The crystal structure changes with temperature, and that changes its conductivity. The resistivity never becomes zero but drops sharply to near-zero. It's so cleanly explained, I can't believe it's not over so it has to be over.