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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

#81

Post by klyrs »

yellowcake0 wrote: post #24

There's a lot of optimism in this thread, but does DFT (or any theoretical model really) actually have much predictive value in quantum chemistry? I've always gotten the impression that in this field the proof is in the pudding.

Explaining why is valuable. The band gap described in this paper is common to other high temperature superconductors. While I remain skeptical, this gives a glimmer of hope, and if the material is indeed superconducting, analysis like this is useful in further understanding high temperature superconductors. If it's not superconducting, then this research may yet be interesting -- if the analysis is correct, it would be interesting to know what's different.

Re: Origin of correlated isolated flat bands in LK99

#82

Post by elfbargpt »

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…

Does anyone know if there's a way to ensure those "particular Cu substitutions" happen at the correct atomic sites? Or I guess what's the way forward in terms of synthesizing

Re: Origin of correlated isolated flat bands in LK99

#83

Post by carabiner »

dcow wrote: post #64
notfish wrote: post #46

Earlier quoted context omitted.

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.

Why? I've always understood it to be the thing the paper describes.

You say potato... The paper is fucking vague on all counts, from synthesis to result. "LK-99" at this point is understood to be most likely a mixture of compounds. It is not fully defined, it is not one "thing," it's broad proposal that encompasses a family of materials.

Re: Origin of correlated isolated flat bands in LK99

#84

Post by jychang »

elfbargpt wrote: post #82
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…

Does anyone know if there's a way to ensure those "particular Cu substitutions" happen at the correct atomic sites? Or I guess what's the way forward in terms of synthesizing

If you figure out how to ensure it gets dropped at the higher energy subsitution site, you would get a nobel prize as well.

Re: Origin of correlated isolated flat bands in LK99

#85

Post by jacquesm »

dcow wrote: post #80
jacquesm wrote: post #77

Earlier quoted context omitted.

Same molecular structure entirely different crystal lattice. It is the formation that is different not the molecules. C = C. They are technically allotropes: https://en.wikipedia.org/wiki/Allotropy And just like here that's a function of how the bulk carbon got to be formed, under extreme pressure and temperatures or less pressure and temperature. It's the recipe that makes the difference, not the ingredients.

As far as I understand, we're saying the same thing. isomer /'aɪsəmər/ noun a compound that exists in forms having different arrangements of atoms but the same molecular weight I'm using isomer to refer to possible different arrangements of "the LK99 compound". I see you're saying allotropes refers to diamond vs carbon (allotrope referring a single element vs isomer referring to compound). That raises a question, wha…

An isomer can have different valences but still have the same overall chemical formula.

So just for an example (I have no idea how to put a tetrahedron in a comment :) ) a chain of C-C-C-C and C-C=C-C (which you likely can not synthesize) would be an isomer but C-C-C-C in one crystal lattice versus C-C-C-C in another crystal lattice would be allotropes.

The carbon in graphite sits in sheets (hence the possibility to form graphene), whereas the carbon in a diamond always forms three dimensional lattices.

edit nah: bad example, sorry, I can't find a good way to visualize this in text the 2nd C-C-C-C chain should have the last C dangling from the 2nd down.

edit2: examples are wrong, I should have used a more complex molecule for the isomer and the carbon can have either three or four other carbons hanging of it for the allotrope. tricky...

Re: Origin of correlated isolated flat bands in LK99

#86

Post by bawolff »

cubefox wrote: post #23

It's funny to read all those grammatical mistakes in the abstract. They are probably just not native English speakers, but to me it sounds like they were frantically typing the paper as soon as they finally got results after a 20 hour lab marathon and way too much caffeine. :D

It isn't the prettiest prose i have ever read, but no obvious outright mistakes stick out to me. It doesn't read any worse than the average hn comment.

Re: Origin of correlated isolated flat bands in LK99

#87

Post by dcow »

jacquesm wrote: post #85
dcow wrote: post #80

Earlier quoted context omitted.

As far as I understand, we're saying the same thing. isomer /'aɪsəmər/ noun a compound that exists in forms having different arrangements of atoms but the same molecular weight I'm using isomer to refer to possible different arrangements of "the LK99 compound". I see you're saying allotropes refers to diamond vs carbon (allotrope referring a single element vs isomer referring to compound). That raises a question, wha…

An isomer can have different valences but still have the same overall chemical formula. So just for an example (I have no idea how to put a tetrahedron in a comment :) ) a chain of C-C-C-C and C-C=C-C (which you likely can not synthesize) would be an isomer but C-C-C-C in one crystal lattice versus C-C-C-C in another crystal lattice would be allotropes. The carbon in graphite sits in sheets (hence the possibility to…

Just double checking, the definitions I'm finding for allotrope are specific to a single element.

    allotrope
    /'ælə,troʊp/
    noun
    a structurally different form of an element
I'm having trouble finding allotrope used to refer to different forms of a compound.

https://www.differencebetween.com/difference-between-allotro...

Re: Origin of correlated isolated flat bands in LK99

#88

Post by piwi »

dtx1 wrote: post #60
ruined wrote: post #54

Earlier quoted context omitted.

musicians often use them to generate distortion, which is purely an electrical phenomenon. germanium components tend to filter high frequencies and don't clip as sharply as silicon, generating tonal effects that can't really be replicated. but mostly, a lot of early guitar pedals used germanium components, and so they are associated with prestigious historic guitar players. here's a video demonstration. silicon first…

> generating tonal effects that can't really be replicated. Seems my headphones can replicate it judging from hearing the audio. Am I missing something?

There are simulators such a Kemper or neural DSP that can reproduce fairly well any amp, but it is expensive, and imperfect.

When you play on emulation it's difficult to know if it is faithful without having used the original.

Some musician appreciate them, others avoid them.

When you happen to finally get the real gear, you often realize it sounds better, and have a wider range of usage.

The convenience of real dedicate knobs, without menus is unmatched.

There is some pleasure with getting the real thing, and use it by yourself.

Re: Origin of correlated isolated flat bands in LK99

#89

Post by [deleted] »

caesil wrote: post #7

Out of curiosity, since this seems like a real inflection point toward trending in that direction, if it becomes increasingly likely that LK-99 or similar material is indeed a high-TC superconductor, what will savvy people be positioning themselves to do? What are good investments? What companies will be started, or what will existing companies be pivoting toward?

[deleted]

Re: Origin of correlated isolated flat bands in LK99

#90

Post by soligern »

M3L0NM4N wrote: post #71
justrealist wrote: post #15

I really hope this unlocks a class of superconductors and isn't a bizarre oneoff compound, because the EPA of 2023 is not going to let us wire the country with thousands of miles of lead-based ceramic wire.

Wouldn't the insulation/shielding also contain the lead?

It’s going to be in everything if it’s what they say it is. Landfills are going to be full of lead.
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