Origin of correlated isolated flat bands in LK99
arxiv.org
arxiv.org
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 work.
This is a DFT paper, and a band structure that is usually seen in high Tc superconductors just naturally came out. She also talks about the strong electron-phonon coupling that naturally arose from the structure, which is always necessary for superconductivity.
I am, by far, the most excited I've ever been about this being a RT, ambient pressure superconductor.
It seems to my own naive self that if LK99 is the real deal, we mostly just got lucky finding it.
They are doing this sort of thing (that's more of a research institute). The problem is that you are not looking for the compound but for the exact way to manufacture it assuming that the original sample really is superconducting.
Obtaining the training data is also likely to be tricky.
The tricky thing is that you don't actually have that much data so ML is not even close to plug and play. If you want to get results you end up needing to pair ML with a lot of theory and some tricky algorithms to help narrow the search space and even then that space is huge.
Progress is being made but I think we're still at least 5-10 years from CS providing a real inflection in materials discovery.
Once you know the atomic positions you can then do little perturbation simulations to model phonon dispersions or ask electron density questions.
Linear scaling DFT is something way more impactful than room-temperature superconductors. What's next? "Hey, I've used my FTL spaceship to verify the material at those friendly alien's library"?
The fact that there has been no Nobel prize and we didn't spend a week around the web arguing "yes, it works!", "no, didn't work for me", "yes, I verified it!" highly implies that the site is trying to say something different than what we are understanding.
https://www.3ds.com/fileadmin/PRODUCTS-SERVICES/BIOVIA/PDF/b...
1. Computation cost is large. 1 compute task for a small scale ~100 atoms last about 3 days to 1 week on supercomputer.
2. Search space is hugh. For each composition you can have different atomic (or crystal) structure. And here we are talking doping which means introduce impurities into the molecule. Chemical characteristics differs depending on which atom you swap for the impurity. Sometimes you may want to try all places.
3. Depends on initial values. Sometimes the initial value is just bad that the result is totally unusable, then you have tweak a little bit and throw back to supercomputer. This cycle might happen few times for 1 specific formula and structure.
4. Not 100% accurate. Often the resulting numbers are off by a few % or more which is hugh, compare to experimental results. Reason is that the simulation is not full scale, approximation is here and there to reduce computational cost.
Also there's been some people arguing about the particles in a box situation for a loooong time and the most promising approach currently is diffusion.
Inorganic crystal structure database (and there is one database literally this name) is way smaller than what we have for proteins. Also by nature, Transformer is hardly useful for crystals because the crystal is repetitive. You don't throw the same sequence over and over to transformer and hope it will work like magic.
My current understanding is that Graph Neural Network is perfect for this job because graph can exactly describe this kind of repetitive nature of crystal.
It's hard enough to get out the hyperfine interaction to the right order of magnitude of a simple metal complex, let alone something like superconductivity, which fundamentally is a many, many body problem...
People vastly over-estimate what we can simulate at any level of fidelity with any scale below purpose-built stuff running on supercomputers..
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.
Edit: s/isomer/polymorph
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.
isomer
/'aɪsəmər/
noun
a compound that exists in forms having different arrangements of atoms but the same molecular weight
That raises a question, what's the name for different crystalline structures of the same compound? Is that still an isomer or something different? I'm out of my element here.
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...
allotrope
/'ælə,troʊp/
noun
a structurally different form of an element
https://www.differencebetween.com/difference-between-allotro...
You're looking at the word "polymorph": "(chemistry, geology) Any substance or mineral that forms different types of crystal."
They found a new phenomenon, that took years to explain. They didn't do anything bad.
Semiconductor yield at high end fabs can be lower than 20%. If you tried that process at a new fab and wound up with a complete failure, would you say "well that process just doesn't produce any semiconductors" or would you think you might need to refine the implementation of the process.
/me skeptical either way
If we have the ability to computationally determine these things without any experimental data needed, and we know we're looking for a specific band structure, wouldn't we just do an automated search of possible chemistries to find everything producing said band structure?
Then just whittle down that list to the easiest to produce and most common materials for the first to test... what am I missing?
Isn't this a plot point in that one Star Trek movie (episode?) where they go back in time and program a current-day computer to do this?
edit: OK, I misremembered. Was thinking of this: https://www.youtube.com/watch?v=LkqiDu1BQXY
Google is doing XC-functionals and Alphafold. Facebook catalysts.
Is the solid state theory space similarly underdefined that you can find a theory for every result? Or is this paper significant?
Then I remember I'm further along the tech tree than they were, and what a gift that is. It's very exciting to watch it update in real time.
Now I'm envious of future generations (I think humanity has a bright future despite the current gloom groupthink).
In the last paragraph before acknowledgements, they point to a feature that could make synthesis difficult, then conclude with "Nevertheless, I expect the identification of this new material class to spur on further investigations of doped apatite minerals given these tantalizing theoretical signatures and experimental reports of possible high-TC superconductivity."
(I'm a high school dropout, worked for a physics project once)
OK I'm starting to actually believe that LK-99 might be the real deal.
Is there a way to force the Cu to the correct site? Or is looking for a new material with similar properties the way forward
There will be thousands of people working on this now. These guys are the shoulders they all stand on.
Better yet, do something like a microwave oven tuned to Lead’s resonant frequency to encourage all the sites to be in the higher energy state as the crystal structure is forming.
For context, the preparation of tetrataenite was pursued for decades (first partial success October 2022) even though the structure was well-known and the constituents are just nickel and iron.
(N.b., I know I’m displaying unreasonable hubris and it’s still more likely than not an illusion or fabrication, but it certainly feels a lot of long term investments are rapidly coming to a head - AI, space, cancer treatments, aging research, EV, even flying cars and fusion - what a great time to be alive)
If it’s brittle as f, then it limits its applications for example.
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.
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, then halfway through they flip the switches and play the same circuit with germanium components.
Seems my headphones can replicate it judging from hearing the audio. Am I missing something?
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.
But then again there's nothing wrong with people romanticising stuff as long as it's more "valves are cool because they're retro and nostalgic" over "valves are cool because they're objectively better".
Guitarists today still use tube amps and germanium transistors (in guitar pedals) for two reasons. The first is that most guitar amps back in the day used tubes (mostly) and the early guitar pedals used Germanium. Guitarists wanted to sound like the earlier musicians that used that technology [1] so they want to use that technology to achieve a certain tone with their instrument. The generation after them wanted to sound like them, so that means old tech for them, too! Repeat until today.
The second reason is that an electric guitar is a combination of a physical and electrical system, and the distortion that is essentially synonymous with electric guitars [2] comes from pushing an amplifier out of its “intended” linear regime [3] into the nonlinear regime where it stops amplifying and starts clipping the signal. The way this nonlinear regime varies with the choice of tubes and transistors, but in general you can’t really replicate one with the other. These unique non linearities impact both the output sound and, most importantly to me as a player, the way the amplifier responds to my physical technique (e.g., how the sound varies with how hard I hit a string). I have played solid state amps that aim to emulate tube amps, and to me the biggest difference isn’t the sound but that physical response. I haven’t played the top of the line modeling amps, but this has been my main problem with the practice amps I’ve tried. As a result, if I’m not playing in my bedroom (pushing a tube amp to distort at apartment friendly volumes is hard), I play through a tube amp. The differences between silicon and germanium transistors are similar, but more subtle and I’m someone who owns a lot of pedals and is constantly switching them out to fit my mood.
[1] an interesting counter example is that the Beatles used early solid state amps on at least some albums
[2] Plenty of people play “clean” without distortion, but if you spend time on guitar forums, you see a lot of beginners who ask a question of the form “I just got my first electric guitar, why doesn’t it sound like an electric guitar?”
[3] Early on the goal was to produce high headroom amps that didn’t distort, but this was very challenging. Rock musicians latched on to the distorted sound and then that became a design feature in later amps. However, if you try to make like a 59 Bassman distort, you have to play it loud enough to kill someone. You can also achieve distortion in other ways, e.g. clipping diodes, but that’s not really germane to this discussion.
Compared to the steps that have been happening in the last decades this one would be absolutely incredible in terms of temperature range, if I understood it correctly they aren't even sure about the upper limit due to a restriction in their measuring gear.
Open-ended research grants to anyone with moderate training in experimental science to just throw shit against the wall and try every last possible combination of something, without concern for 'publish or perish' or jockeying for status in academia. Lets get our smartest and most dedicated technical people back in labs rather than off making CRUD apps for 10x academic wages.
If this discovery is true, we just got lucky. Based on the story we know of LK-99 it almost didn't happen, and our current system is not set up to make these kinds of discoveries quickly. Throwing billions at 'just go find stuff that matters' basic research is ultra cheap in comparison to humanity not having a high-tc superconductor.
* 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 would do better)
* EVs: improved performance of motors, batteries, charge time, and weight - huge shift for the market. Much safer than most current car batteries too.
* Big breakthrough for computing in the form of fast, cool, and efficient zero-resistance transistors. Step change for cutting-edge component performance, all the cloud hyperscalers would completely revamp their compute. TSMC / ASML probably get huge volumes of new orders.
Obviously the first bet is following the patents. Otherwise, my play would be the industrial companies that build things that build things, like factory automation companies, followed by companies that would see a surge in demand from products incorporating room-temp superconductor technology, like TSMC, ASML (maybe Apple/AWS).
https://ieeexplore.ieee.org/document/783712 (770 GHz toggle flip-flop in 1999)
https://www.physics.sunysb.edu/Physics/RSFQ/Projects/WhatIs/...
https://www.youtube.com/watch?v=3O6GpFCIxv0
...and...
Storage would help, the cheapest production cannot run continuously.
Superconductors could make transmission lines much more compact, sturdy, weatherproof, and less vulnerable to sabotage. You could run a thick armored cable instead of a set of open-air wires on tall towers.
We will still need some step-downs, because current density is limited. But we will need fewer of them, and they won't need the monumental cooling they have now.
I agree that the nature of this is entirely different to transmission losses, but I don't expect 230V lines carrying tens of thousands of amps. This would probably require excessive amount of SC material.
Generating costs are a small fraction of the final price of electricity, taxes and transportation are the big ones.
If you just look at superconductors as a replacement for any old piece of wire you're going to miss out on a whole bunch of advantages, it is a clear qualitative difference which enables solutions that are entirely undoable today. Yes, there is HVDC, but the lines are expensive and due to the high voltages involved are not easy to interface to or from. They do have some unique advantages, being DC they allow non-synchronized grids to be connected.
The whole "plate a desert with solar power and solve the world energy problems" doesn't work because the desert isn't where the power draw is. Superconductors hypothetically permit the African desert to supply Europe with power.
As this goes from science to engineering, we may find other issues with that plan, beyond the obvious expenses (for example, current limits can be handled with more wires, but if the current limit is sufficiently small that's still a problem, this is no solution if the superconducting bundle has a hundred square meter crosssection), but superconductors at least put it on the table. Conventional conductors do not.
1) This is simulation result using density functional theory. While a standard method for understanding the electronic structure of materials it often does not do so accurately when correlations (electronic interactions) are strong. In this kind of context (where strong interactions are expected to be necessary to give something like high temperature superconductivity) what one is looking for from a DFT simulation is an indication of what kind of starting point to extend further and include interactions.
2) What is seen here are features called "flat bands". Essentially, the kinetic energy of the electrons relevant at low energies is only weakly dependent on the (crystal) momentum of the particle. Having lots of different states (different momenta) at similar energy usually means the interactions are more important than in materials where the kinetic energy is larger and more dispersive (depends more strongly on momentum). Here the partially filled d-shells of the Cu atoms appear to make a flat band at low energy. This flat band is partially filled and thus is potentially susceptible to interaction induced instabilities.
3) Flat bands can come from trivial features of a crystal as well. If you've got isolated atoms far apart enough that their atomic orbitals barely overlap their bands will be flat. Some of this may be at play here since the Cu atoms seem to be quite distant (7-9 Angstroms or so).
4) Flat bands appear in many many kinds of systems (at the level of DFT, even at the level of experiments, etc, etc) and do not necessarily imply superconductivity, let alone high temperature superconductivity. Even if the presence of flat bands is pointing towards stronger and more important interaction effects these interaction effects can stabilize other kinds of order instead (magnetism, charge order, etc).
5) Predicting what instability is realized is hard and can be quite delicate. There are materials where this can be debated (theoretically and sometimes experimentally) for years. Predicting the onset temperature of the order that is produced is hard. I.e. Don't necessarily expect a reliable estimate of the critical temperature from theory.
That's true, but are there superconductors that do not have those flat bands?
If not then it wouldn't be evidence that it is superconducting but it would at least check one more expected property (based on the evidence obtained about superconductors so far).
Yes, many. Most (all?) conventional superconductors. High-Tc iron arsenide superconductors discovered ~15 years ago. DFT (without including Hubbard "U" type corrections) for the cuprate high-Tc superconductors also doesn't indicate show flat bands.
Examples that do have flat bands (or similar physics) include the recently discovered twisted bilayer graphene (still very much actively studied), as well as (morally speaking at least) heavy-fermion superconductors (too many to list).
Superconductivity is a phase of matter than can arise in a variety of different ways depending on the details of the underlying physics. So at least when talking about the microscopic mechanism that stabilizes the superconducting state there isn't any single theory or one set of predictions/properties.
Thanks!
That's radically different from searching for a compound with particular properties, that is a much more error prone process.
"I don't like the waiters in this restaurant"
"Have you ever eaten here?"
"Oh. No. I mean the other restaurant."
"Which restaurant?"
"I mean one of those other restaurants in town. Don't like 'em. They talk funny."
But even if it is just superconducting grains smaller than a millimeter that would already be a massive discovery.
Because I can guess how you'd go about doing the first bit: crush it, put a magnet under it, and scrape off any bits that float...
Based on the early successes shown by applying social media platforms like Twitter, Twitch, Discord, etc, to accelerating science, I hope we can evolve better tools and platforms which are equally open but even more suited to the exchange of scientific ideas, results, review and feedback.
One caveat tho is that hype can also distort and there's a limited resource of 'the public's excitement with science' that depletes if it never delivers, so I wouldn't necessarily couple science education/comms with science process so tightly. Most science is lots and lots of boring toil, and I'd hope the $$s flow to the best scientists rather than the ones who tell the most twitter-friendly stories.
Korea should protect its students and their work a little more if they want their own TSMC, Texas Instruments of Korea doesn't sound right
I don't want scientists to be turned into influencers or D-grade celebrities having to debase themselves on shows like Joe Rogan in order to get funding or justify their work. Or what happened this week on Twitter where the scientist was obsessed with trying to get above 15m views so he could get monetised.
It is great to learn more about the scientific process in this ad-hoc manner but I would prefer to let scientists figure out themselves what works best for them rather than it being driven from the unwashed masses.
LK99 is reinvigorating broader interest in science, and this may be one of the most important things that could possibly happen at a moment in our global history that desperately needs broad support for research and progress. None of this matters if we don’t sort out some pretty major climate/energy problems, and soon.
I agree that it would be problematic for science to become what you describe. What you describe is not some guaranteed outcome of a shift towards more public participation and awareness.
And to be honest, if it does lead to some garbage behavior, that may be a small price to pay for getting the public interested and invested in the process of progress.
Not everyone is addicted nor has the personality to start becoming livestreamers over some experiments.
e: oh wow holy crap manifold has a lot more liquidity than when I last checked in, sold for an easy profit now that I think it has returned to a more reasonable probability
I am making a political claim that bureaucrats will behave in certain, highly predictable ways.
If the material proves to be what it claims to be, it will not be banned. At most, it will be highly regulated, as that will preserve and expand government power.
Once the cable is laid, it's a liability.
We don't have reliable process to produce them in large quantity
It just needs proper handling and isolation.
For example, if we can transport electricity with a super conductor over long dsitances (1000 of kms), then what happens ? Is it just an incremental progress or is it a huge breakthrough ?
(I am not much trained in physics)
Or click here: https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...
Energy efficiency is just one gain. This also potentially unlocks major gains in quantum computing, fusion energy, tradition computer chip design allowing another 30 years of moore’s law, batteries with zero energy loss leading to ultra dense batteries and electric aviation
Only the industrial sector could claim exceptions but would still need to comply with safe cleanup and disposal.
So a $2,400b/year opportunity. And that's just from transmission let alone the many other things it can do.
But what effort is needed? Wouldn’t it require replacing all batteries and transmission lines to realize this efficiency gain?
A lot of other researchers close to this type of work have come out to say the same. Lots of materials are like that, simulation is still too approximate etc.
https://duckduckgo.com/?q=high+temperature+superconductor+ta...