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Origin of correlated isolated flat bands in LK99

arxiv.org

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Re: Origin of correlated isolated flat bands in LK99

#41

Post by dcow »

jacquesm wrote: post #36
dcow wrote: post #31

Earlier quoted context omitted.

It doesn't reproduce: https://arxiv.org/abs/2307.16802 . That doesn't mean there's not something to further investigate, but LK-99, at least as described in the paper, is not it.

It doesn't reproduce in that case, which is a useful data point but may not be the final word. The article linked in this thread suggests why making it may not be all that easy.

I'm just saying that it's not really LK-99, then. It's something else that needs to be specified more precisely.

Re: Origin of correlated isolated flat bands in LK99

#42

Post by dcow »

pengaru wrote: post #37
dcow wrote: post #31

Earlier quoted context omitted.

It doesn't reproduce: https://arxiv.org/abs/2307.16802 . That doesn't mean there's not something to further investigate, but LK-99, at least as described in the paper, is not it.

What the simulation is saying though is that it requires some luck, not all the arrangements result in the band structure.

I understand. I'm saying that it's not LK-99 as described, then. Rather, it's something else that needs a more precise specification.

Re: Origin of correlated isolated flat bands in LK99

#43

Post by ivalm »

bibabaloo wrote: post #30
raziel2701 wrote: post #10

Man, I'm feeling stronger about LK-99 being it. This paper is theoretical and she finds that particular Cu substitutions onto specific Pb atomic sites are key to enabling a band structure that is usually linked to high Tc superconductors. What this means for the more practical minded is that the synthesis of superconducting LK-99 is not trivial and you need to make the appropriate substitutional alloy for this to wor…

If this could be simulated, can you help me understand why we couldn't have used simulation to find promising SC materials to investigate further earlier? Are there just too many permutations to investigate? It seems to my own naive self that if LK99 is the real deal, we mostly just got lucky finding it.

You have to put in the structure and then it's expensive to do the calculation. The space of possible structures is extremely large. If you have candidates then you can run through them, but you can't just random search through trillions of trillions of candidates.

Re: Origin of correlated isolated flat bands in LK99

#44

Post by montecarl »

mrandish wrote: post #6
dtx1 wrote: post #3

Even if LK99 turns out to be a dud, it's proven that there's a great need and great opportunity for more direct communication from scientist on their experiments via the internet. Live Stream of the Synthesis, Twitter Threads giving life updates of different teams, etc.

I fully agree that the traditional journal and academic publishing models are having significant negative impact on the conduct of science. I also really like that the Arxiv, open access publishing, open peer review, live science and similar new models represent a refreshing return to less gatekeeping, politics and institutional gamesmanship. Based on the early successes shown by applying social media platforms like…

Most science is way too boring and requires way to much work to reproduce to follow this kind of model. This open science type work we are seeing for LK-99 works fantastically when a huge number of scientists are interested in the problem and motivated to study it. Most papers aren't even cited more than a dozen times if that.

Re: Origin of correlated isolated flat bands in LK99

#45

Post by tired_and_awake »

bibabaloo wrote: post #30
raziel2701 wrote: post #10

Man, I'm feeling stronger about LK-99 being it. This paper is theoretical and she finds that particular Cu substitutions onto specific Pb atomic sites are key to enabling a band structure that is usually linked to high Tc superconductors. What this means for the more practical minded is that the synthesis of superconducting LK-99 is not trivial and you need to make the appropriate substitutional alloy for this to wor…

If this could be simulated, can you help me understand why we couldn't have used simulation to find promising SC materials to investigate further earlier? Are there just too many permutations to investigate? It seems to my own naive self that if LK99 is the real deal, we mostly just got lucky finding it.

DFT scales horribly so it's phenomenally expensive to run. You have to have some other mechanism for knowing the general atomic layout before entering the DFT realm.

Once you know the atomic positions you can then do little perturbation simulations to model phonon dispersions or ask electron density questions.

Re: Origin of correlated isolated flat bands in LK99

#46

Post by notfish »

dcow wrote: post #41
jacquesm wrote: post #36

Earlier quoted context omitted.

It doesn't reproduce in that case, which is a useful data point but may not be the final word. The article linked in this thread suggests why making it may not be all that easy.

I'm just saying that it's not really LK-99, then. It's something else that needs to be specified more precisely.

Defining LK-99 as “the thing you get from following the steps in this paper” and not “the allegedly superconducting material these guys have a sample of” is silly.

Re: Origin of correlated isolated flat bands in LK99

#47

Post by bpye »

jakeinspace wrote: post #40
losteric wrote: post #26

Earlier quoted context omitted.

Posting for Cunningham's law :) * Green energy suddenly becomes way more viable. Megaprojects in the most efficient sites can send energy long-distance and store it with effectively no loss, somewhat mitigating regional variations (especially if we have a high-trust world order where a united global grid is viable). (I read LK99 might have some limitations carrying lots of current but presumably other approaches woul…

Sorry, but how does one create a transistor from a superconductor? Maybe I’m missing something here.

I don’t think we’d necessarily have to use it for transistors, but could use it in place of the metal interconnect that is significant in terms of resistive loss.

Re: Origin of correlated isolated flat bands in LK99

#48

Post by Ccecil »

bick_nyers wrote: post #18
tnecniv wrote: post #16

Earlier quoted context omitted.

And audio nerds everywhere are still lusting after germanium transistors to this day!

Could you explain why? Sounds intriguing.

My understanding is that it is due to the lower voltage drop across the base junction. Germanium is .3v vs Silicon .7v, so with germanium you get less "crossover distortion" when the input signal is crossing the 0 line.

edit: I understand that typically this is biased out with diodes...but the matching is not perfect and it is easier to start with half the distortion.

Re: Origin of correlated isolated flat bands in LK99

#49

Post by bacon_waffle »

tnecniv wrote: post #16
dtx1 wrote: post #14

Earlier quoted context omitted.

Even if it is, we can coat it in epoxy and deal with it. And even if we can't, remember the first semi-conductor was germanium. If we have a theoretical and practical reproducible RT Superconductor we will very fast find new, better ones.

And audio nerds everywhere are still lusting after germanium transistors to this day!

Hmm, superconducting inductors seem like an audiophile thing. Patent?

Re: Origin of correlated isolated flat bands in LK99

#50

Post by jacquesm »

dcow wrote: post #41
jacquesm wrote: post #36

Earlier quoted context omitted.

It doesn't reproduce in that case, which is a useful data point but may not be the final word. The article linked in this thread suggests why making it may not be all that easy.

I'm just saying that it's not really LK-99, then. It's something else that needs to be specified more precisely.

I'm not following you. The compound is specified, the process is what is poorly specified and the researchers more or less admit that they do not exactly know what the right method is. This makes it a lot harder to replicate and may well cause a lot of attempts to misfire before someone finds something that works or we give up on the search. What TFA here suggests is that there are some potential complications in manufacturing this that would explain why the original researchers had problems trying to make the compound, the number that I recall is that '1 in 10' tries resulted in a working sample.

That would also be a fantastic way to pull a hoax, because it will result in 10x more effort spent on your hoax. If it turns out that it was a hoax I think the original researchers will find immense gratitude from Pons and Fleischmann for taking over the top spot for the textbook example of bad science. But for now, as far as I can see the jury is still out, and if anything the paper linked here actually improves the chances of it being real a bit more than it is offset in the other direction by a failed replication attempt.

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