LK99 -- A new room temperature superconductor?

Found this, can't remember where, if not related please delete....

2307.16892.pdf

Quote from jox

Found this, can't remember where, if not related please delete....

2307.16892.pdf

Is someone trying to explain theoretically where and how the superconductivity could be produced in this materials, if the claims are true. So it is certainly related.

I honestly had not taken much interest in this topic as I think is too early to have a sufficiently backed up opinion. That said, the paper just posted by jox is being touted as a sort of independent replication as it was produced using LANL state of the art simulation software.

Also, a Chinese team claims to have replicated the Meissner effect.

Found this page where there’s someone devoted to collect information on replication, and one can see the Chinese team video that is somewhat less than convincing.

Tracking LK-99 Superconductor Replication Efforts With Meissner Effect | NextBigFuture.com

Huanzhong Univesity and Iris Alexander claim to have replicated and seen some Meissner effect. Berkeley Lab and Shengyang lab have separate theory papers with

www.nextbigfuture.com

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Is someone trying to explain theoretically where and how the superconductivity could be produced in this materials

My take is here. It's 1D semiconductor.

I know August is meant to be a slow news month - but Twitter TwiX has gone LK-99 crazy.

Quote from Frogfall

I know August is meant to be a slow news month - but Twitter TwiX has gone LK-99 crazy.

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I for one welcome anything that launches such a craze of interest in scientific matters, however people paying attention to such topics, sometimes, get carried away as much as people that is rooting for a sports team, and the level of the discussion can become ridiculous and surrealistic. Anyway, at least is far more interesting than celebrity gossip / crime and politics (at least for me), which seems to be all mainstream is carrying nowadays.

Quote from Zephir_AWT

My take is here. It's 1D semiconductor.

None of your linked post mentions "1D superconductors". Did you forget to give your take? Plus it makes no sense anyway since the universe is (at least) 3D. Nothing is truly 1D except in math models.

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None of your linked post mentions "1D superconductors". Did you forget to give your take?

Whole this paragraph deals with it. In last two days there are have been at least four studies that help explain LK-99's potential superconducting abilities. These simulations converge on key properties that suggest a new class of SC materials, and help explain quirks of TK-99 we've seen so far. Here is the easy-to-digest summary:

This effect relies on copper replacing lead atoms in the crystal, but it has to replace very specific lead atoms for the bands to appear, meaning it may be hard to synthesize with high purity. The conduction pathways in the material may be one-dimensional, meaning they aren't equal in all directions, and this could be why it doesn't act as a perfect magnetic levitator but rather a semi-levitator. Also, other metals like gold could make LK-99 perform even better. TK-99 appears to be much more robust to disorder, or randomness in the crystal, while retaining its superconducting properties. And, it appears the overlap of copper and oxygen electron orbitals might explain why this occurs at ambient pressures. The appearance of diamagnetism without superconductivity seems unlikely.

Before some time I proposed mechanical model of superconductor. It's formed by insulated wire enclosed in vacuum against counter electrode with low electron emissivity. By placing sufficiently high voltage we can achieve the situation, when free electrons will collect on the surface of insulator and create a compact, possibly superconductive layer there:

IMO new superconductor works similarly. Instead of wire attracting electrons there are long lines of oxidized copper atoms Cu(3+), so-called hole stripes. They're enclosed with channel in crystal lattice of apatite columns, so that the electrons from outside can not get into direct contact with it. They pile-up around Cu(3+) copper ions like hungry hens around elongated feeders, fighting for their position and enabling propagation of charge in density waves instead of individual electrons or Cooper pairs.There are also know organic polymer based ultraconductors, which work similarly at even larger macroscopic scale.

Good update:

A Room-Temperature Superconductor? New Developments | Science | AAAS

I'm doing this as a follow-on to my previous post on this topic, since this is a fast-changing story. To recap, preprints appeared last week making the remarkable claim of a well-above-room-temperature superconducting material at ambient pressure, dubbed LK-99.

This is one of the most sought-after goals in all of materials science and condensed matter physics, something that until now has only been found in (numerous!) science fiction stories. The potential applications of such a material almost can go without saying - depending on what current density it could accommodate, it could improve almost anything that uses electromagnetism.

Well, extraordinary claims need extraordinary proof, and where things like this usually fall apart is difficulty with replication. The experimental preparation of LK-99 was not very complicated at all, though, and did not use any particularly exotic materials or equipment, so the expectation was that many labs would immediately try to reproduce it. There are always complications, of course: even the original authors said that their samples were polycrystalline and heterogeneous, and there is no expectation that the reported preparation is an optimized one. (Whether the authors have a better one that is yet unpublished is an open question!) This means that replication might not be a smooth process, but it also means that a lot of people will be giving it a try, increasing the chances for success even if there are variables that we don't yet appreciate. Even the ones we do appreciate (starting material purity, presence of oxygen, particle size, heating and cooling rate, size/shape of the vessel) are enough to give you a lot of variability, I'd say.

Another complication has been some apparent infighting among the authors of the preprints. The two manuscripts appeared in close proximity, one with three authors and one with six. As I understand it (subject to change!) reports are that the three-author preprint might be withdrawn, supposedly because one of the authors submitted it without consulting with some of the others, and that the six-author one is now being readied for submission to a peer-reviewed journal (the preprint itself has already been revised). It may be a while before we understand what has actually been going on behind the scenes, but honestly, I can't blame anyone for some excitability and confusion. If I'd been in on the discovery of a room-temperature superconductor I would have surely have gone into Headless Poultry Mode myself.

The Latest, As of August 1

As of this morning, there are (as yet not really verified) reports of replication from the Huazhong University of Science and Technology in China. At least, a video has been posted showed what could be a sample of LK-99 levitating over a magnet due to the Meissner effect, and in different orientations relative to the magnet itself. That's important, because a (merely!) paramagnetic material can levitate in a sufficiently strong field (as can diamagnetic materials like water droplets and frogs), but these can come back to a particular orientation like a compass needle. Superconductors are "perfect diamagnets", excluding all magnetic fields, and that's a big difference. The "Meissner effect" that everyone has been hearing about so much is observed when a material first becomes superconductive at the right temperature and expels whatever magnetic fields were penetrating it at the time. All this said, we're having to take the video on the statements of whoever made/released it, and there are other possible explanations for the it that do not involve room-temperature superconductivity. I will be very happy if this is a real replication, but I'm not taking the day off yet to celebrate just based on this.

And even though I'm usually more of an experimental-results guy than a theory guy, two other new preprints interest me greatly. One is from a team at the Shenyang National Laboratory for Materials Science, and the other is from Sinéad Griffin at Lawrence Berkeley. Both start from the reported X-ray structural data of LK-99 and look at its predicted behavior via density functional theory (DFT) calculations. And they come to very similar conclusions: it could work. This is quite important, because this could mean that we don't need to postulate completely new physics to explain something like LK-99 - if you'd given the starting data to someone as a blind test, they would have come back after the DFT runs saying "You know, this looks like it could be a really good superconductor. . ." Here's Griffin:

I present the calculated spin-polarized electronic structure in Fig. 3. Remarkably, I find an isolated set of flat bands crossing the Fermi level, with a maximum bandwidth of ∼130 meV (see Fig.4) that is separated from the rest of the valence manifold by 160 meV. Such a narrow bandwidth is particularly indicative of strongly correlated bands. . .unlike other correlated-d band superconductors, in this system the Cu-d bands are particularly flat – there is minimal band broadening from neighboring oxygen ions. If previous assumptions about band flatness driving superconductivity are correct, then this result would suggest a much more robust (higher temperature) superconducting phase exists in this system, even compared to well-established high-TC systems.

If you're not a solid-state band theory person (no disgrace!), the Fermi level is the theoretical energy for an electron in a solid material where it would have a 50% chance of occupying that energy level at any given time - sort of the "natural home" for mobile conducting electrons in a given material. Electrons in solids are modeled as occupying a series of "bands" of different energies, separated by band gaps. If a material is an insulator, that means that its Fermi level is sitting inside a wide band gap, and its electrons will not be able to give you any current. Metals, on the other hand, have one or more bands that land at the Fermi level (in semiconductors, in case you're wondering, the Fermi level sort of "grazes" the bands, close enough to where thermal energy can move some electrons into them).

Griffin's paper goes on to say that these results hold for substitution of copper atoms into the Pb(1) location in the lead apatite structure, as reported by the original preprints, but that her calculations suggest that substitution into another location, Pb(2) seems to be energetically more favorable, "suggesting possible difficulties in robustly obtaining Cu substituted on the Pb(1) site". This then would be a source of variability in reproducing LK-99, or at the very least in getting a particularly clean bulk sample of it.

Meanwhile, as mentioned the Shenyang group has very similar conclusions (as they should; both they and Griffin are using the same DFT software package!) The starting lead apatite is a very good insulator, but the structural changes on bringing in the copper atom both match the experimental data from the Korean preprints and lead to a very large shift to a metallic state. They find a half-filled flat band and a fully-occupied flat band around the Fermi level, and agree that these are crucial to investigate for the reported superconductivity. They also predict that substituting gold atoms into the Pb(1) site could lead to a material with very similar properties, which will be an extremely interesting idea to put to the test. Here's more from their preprint:

In addition, the PO4 units surrounding the cylindrical column formed by Pb2 atoms also exhibit insulating characteristics, leading to a one-dimensional-like conduction channel along the c axis mediated by the 1/4-occupied O2 atoms. More interestingly, we observed four VHSs on these two flat bands, originating from the saddle dispersions at the M and L points in the Brillouin zone [see Figs. 2(e), (f) and (g)]. This indicates that the electronic properties are fragile in response to structural distortions at low temperatures.

They don't go into the possible lower-energy substitution at the Pb(2) site, but the above warning about fragile electronic properties might also explain some of the variability in the behavior of the material (although it has to be balanced with the original report of superconductivity up past the temperature of boiling water!) It also highlights something that occurred to me when I read the original preprints: if you could grow a good single crystal of LK-99, it seems as if the superconductivity might only occur along one crystal axis: put crudely, you'd see superconductivity if you hooked your wires to two particular opposite faces of said crystal, but not to the others! Crystalline grain boundaries are already known to be a big deal in the efficiency of existing superconducting materials, and this would mean that polycrystalline samples of LK-99 would be pretty unfavorable to demonstrating robust effects.

Conclusion

I am guardedly optimistic at this point. The Shenyang and Lawrence Berkeley calculations are very positive developments, and take this well out of the cold-fusion "we can offer no explanation" territory. Not that there's anything wrong with new physics (!), but it sets a much, much higher bar if you have to invoke something in that range. I await more replication data, and with more than just social media videos backing them up. This is by far the most believable shot at room-temperature-and-pressure superconductivity the world has seen so far, and the coming days and weeks are going to be extremely damned interesting.

Southeast University of China made 6 batches of samples, one seemed to be promising. Probably the first video of new superconductor levitation (backup) exhibiting actual magnetic flux pinning - the only problem is, its Chinese source is unverified... Verification of superconductive properties proceeds successfully too.

A skin effect at Thz range could be a way to consider too ?

Quote from Zephir_AWT

By placing sufficiently high voltage we can achieve the situation, when free electrons will collect on the surface of insulator and create a compact, possibly superconductive layer there:

If is great fun just to see Shane getting so excited.

It is like one of those YouTube videos watching somebody who is watching a movie.

But we all have our fingers crossed, such landmark advances in science are rare and hard won.

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A skin effect at Thz range could be a way to consider too

This is DC effect - electrons get attracted to a surface of insulator. Recently we discussed here energy storage device based on similar arrangement.

This Corean team who developped this LK99 talked about 100°C as temperature limit !

That implies a simple water cooling to maintain this threshold..

For completeness, before some time J.F.Prins observed room temperature superconductivity in similar arrangement. But the people are of short memory and attention span, so that they're predestined to invent the same things again and again (so that more people can keep their jobs).

It reminds me also the surface plasmon ...

Quote from Zephir_AWT

For completeness, before some time J.F.Prins observed room temperature superconductivity in similar arrangement. But the people are of short memory and attention span, so that they're predestined to invent the same things again and again (so that more people can keep their jobs).