Review
This is a linkpost for https://arxiv.org/abs/2307.12008
Review
The First Room-Temperature Ambient-Pressure Superconductor
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New Comment
I find it curious that it is stated to be a modified lead-apatite structure. The term apetite is derived from the Greek word ἀπατάω (apatáō), which means to deceive. Having said that I truly hope this discovery is real!
Well, it's at least not a Pons and Fleischmann (the cold fusion guys) situation; the paper shows a whole battery of tests, and based on my more-than-random-guy-on-the-street-but-less-than-expert knowledge they sure sound like the right kind of tests. Either they actually found superconductivity, or they're lying through their teeth.
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1The original Pons & Fleischmann paper also had “a whole battery of tests”, namely:
- low-current calorimetry measurements,
- high-current calorimetry measurements (using a somewhat different experimental setup)
- gamma ray spectrum (indirect evidence of neutrons, via the H+n→D+γ reaction)
- measurement of neutron flux (more directly)
- measurement of tritium (more directly)
(Plus other things that they didn’t include in that particular paper.)
Every single one of these claims was erroneous!! For different reasons!! But I also strongly believe that they were reporting their results in good faith. (Gory details can be found in the final post of my old cold fusion blog.)
1Oh interesting, I thought their announcement was based entirely on excess heat in calorimetry and they notably did not have neutron flux, gamma ray or tritium detection results. Is this a difference between the original announcement and the eventual paper, or did I just completely misremember?
This page links the press conference video. I don’t feel like watching it. However, the same page also links to the original press release, which does in fact mention measurements of neutrons and tritium. So I guess that means they already had their nuclear results by the original press conference.
Cold fusion skeptics and cold fusion advocates are united in the belief that Fleischmann and Pons’s nuclear measurements were erroneous. The advocates shrug and say that Fleishmann & Pons were not specialists in those kinds of nuclear measurements, and just messed up. That broad consensus rejection developed pretty quickly after the press conference.
However, the cold fusion advocates continue (to this day) to believe the Fleischmann-Pons calorimetry results, whereas the mainstream consensus (and also my opinion) is that Fleischmann & Pons messed up on calorimetry too.
(Today’s cold fusion advocates do think there exists direct nuclear evidence of cold fusion, but they would cite later experiments by different people; that would be Section 4 here.)
1Seems quite compelling - most previous claims of high temp superconductivity have been based on seeing only dips in resistance curves - not full array of superconducting behaviours recounted here, and sample preparation instructions are very straight forward - if it works we should see replication in a few days to weeks [that alone suggests its not a deliberate scam].
The critical field strength stated is quite low - only about 25% of what is seen in a Neodymium magnet and it's unclear what critical current density is, but if field reported is as good as it gets then it is unlikely to have much benefit for motor design with B² dependent torque densities <10% of conventional designs, unless the applications are not mass/cost sensitive (wind turbines replacing permanent magnets?).
Meissner effect could be useful for some levitation designs (floating houses, hyperloop, toys?) Likely some novel space applications like magnetic sails, perhaps passive magnetic bearings for infinite life reaction control wheels and maybe some ion propulsion applications. But lightly biggest impacts will be in digital and power electronics with ultra-high q inductors, higher efficiency transformers, and maybe data processing devices.
It might be transformative for long distance renewable power distribution.
[Edit to add link to video of meissner effect being demonstrated]
Meissner effect video looks like the real deal. Imperfect disk sample is pushed around surface of a permanent magnet and tilts over to align with local field vector as gets closer to edge of cylindrical magnet end face. Permanent magnets in repulsive alignment are not stable in such arrangements (Earnshaw's theorem) - they would just flip over, and diamagnetism in conventional materials - graphite the strongest - is too weak to do what is shown. The tilting shows the hall-marks of flux pinning working to maintain a consistent orientation of the superconductor with ambient magnetic field, which is a unique feature of superconductivity. No evidence of cooling in video.
If this is not being deliberately faked then I'd say this is a real breakthrough.
(Variant of something I put as a comment on Zvi's blog.)
Yesterday I put up a blog post that walks through the 2 papers on LK-99 superconductivity in the style of what in grad school they call "Journal Club": https://www.someweekendreading.blog/high-tc-sc/
It has all the hallmarks of something very much rushed into publication: misspelled words, awkward phrasing, out-of-order paragraphs, misnumbered figures, and (most charmingly) error messages in Korean from their bibliography software. At this stage of things, all that is understandable and excusable.
A few things are presented in a peculiar way, unlike most of the other sc papers I've read. Again, that's more or less ok once you disentangle the coordinate systems on the plots and the like. It can be fixed easily, and probably will be.
To convince anybody to take you seriously enough to test for superconductivity, you have to demonstrate 4 things: (1) 0 resistivity below a reasonably sharply defined temperature, (2) the existence of a critical current above which transition back to normal occurs, (3) the existence of a similary critical magnetic field, and (4) the Meissner effect, or magnetic flux expulsion (totally for Type I and at least partially for Type II).
They did the first 3 of those reasonably believably (even to a guy like me who still has scars from the cold fusion mishegoss back in the day). The Meissner effect, though, gets only partial credit: the diamagentism for the field-cooled & non-field-cooled samples implies an unphysical value of the diagmagentism, and the picture/video of a sample on a magnet only sorta-partially levitates.
The diamagnetism curve has apparently been addressed, as the authors say it was simply a copy-paste error on the graph. The Meissner effect visuals could be explained by the fact that they have a polycrystalline sample (resistance between domain boundaries) of unknown impurities (sometimes coppuer sulfides, other times the Pb/Cu doping may vary across the sample). (Again, this is totally excusable given the rush.) When other people start preparing samples, we'll see what's happening here.
It's not going to revolutionize anything in its current early form:
(1) Frankly, it looks like charcoal. It's almost certainly not ductile enough to form a wire, and any long thin sample that looks like a wire would be too brittle to wind into a coil.
(2) The critical magnetic field is pretty low, maybe 0.3 Tesla at room temp. For comparison, the tokamak magnets being used by Commonwealth Fusion Systems for their prototype reactors weigh in at 20 Tesla.
(3) The critical current is low. The right thing is to report a current density, but they only report total current without information on sample shape. Still, they topped out at around 250 mA. For comparison, the CFS tokamak magnets run around 40 kA.
IF IT REPLICATES, it's a fascinating step in phyics (mechanism proposes stressed crystals forming an array of superconducting quantum wells, with currents forming by electron tunneling along the Pb metal backbone... maybe).
But as it is, it's not an engineering material.
THAT IS ABSOLUTELY OK! This is an early stage compound, all it has to demonstrate that it works. Then tons of material scientists and physicists will start tweaking the recipe, to optimize transition temperature, critical current, and critical field.
Also, I hope, somebody will figure out how use something other than lead. Right now it doesn't use rare earths, which is good. But it would be better if we could use something with a similar crystal structure to the lead apatite (Lanarkite), but less toxicity.
Then last night all hell broke loose. Kwon made a conference presentation. During that, Lee and the other authors more or less disowned him, said he was fired from the university and the company, and that the first paper was an unauthorized upload by Kwon. Then they retracted the first paper that Kwon apparently wrote on his own and uploaded.
Drama drama drama.
I'm waiting for Argonne, which seems to be on deck for a replication trial next week.
Absolutely! It's not ductile enough for wire, and too frangible to bend around a coil even if you managed to make a long thin piece.
But... the early high-Tc superconductors in the 80s were ceramics, too. Even now, with much more friendly materials, the "wire" in the Commonwealth Fusion Systems tokamak prototype is actually a complex tape with multiple layers mostly for structural support.
Some details here: https://spectrum.ieee.org/fusion-2662267312
Here's a very nice, more technical presnentation at Princeton by a CFS person, showing the tape strucdture, and how the material had to evolve from microcrystalline stuff to much more complex forms to be useful in an engineering sense: https://suli.pppl.gov/2020/course/20200619_SULI_HTS_Sorbom_Final.pdf
Also note: fusion-relevant REBCO magnets operate at 20T fields and 40kA currents, whereas this new superconductor can't get above 0.3T fields and 250mA current. Lots of work to do there!
So I hope that gives the right idea: getting from today's charcoal lump/floaty rock to something with optimized chemistry, easier manufacturability, ductility close enough to wire, and deployable in high fields & high currents took about 30 years the last time it was done.
It'll be quicker this time, getting from the current charcoal to whatever works, because the incentives are higher. But it almost certainly won't be simpler.
Provided the paper is legit, what are the implications on AI timelines? Would compute-intensive paradigms like WBE suddenly become feasible?
Someone from South Korea is extremely skeptical and wrote a long thread going into paper's details why it must be 100% false: https://twitter.com/AK2MARU/status/1684435312557314048. Sorry it's in Korean, but we live in the age of miracle and serviceable machine translation.
Considering a lack of peer-reviewed acceptance, the absence of crucial data points in their study, and past instances of similar unverified claims, skepticism is warranted. Applying Bayesian reasoning to the provided information, I propose an initial estimate of 10% for the probability of these claims being validated. This conjecture is subject to change as more evidence becomes available or if replication efforts are successful. For now, the principles of scientific rigor and healthy skepticism guide us to a cautious optimism. In conclusion: In light of the evidence available on the supposed room-temperature superconductor, LK-99, caution is advisable. Several red flags, including lack of peer review and missing critical data, suggest skepticism. Considering these factors, the likelihood of this claim being substantiated appears to be around 10%. Just to be clear, that still a huge achievement, we are 10% closer to the holy grail, considering all possible cenarios.
1I'm not sure you can call someone else's work a "huge achievement" based on your own uncertainty about whether their conclusions are correct.
https://archive.is/2023.07.26-181113/https://www.newscientist.com/article/2384782-room-temperature-superconductor-breakthrough-met-with-scepticism/
They link a video ( https://archive.is/GLKS8 ) in that article. I can't get it to play for some reason, but I think that is a really positive update towards it actually being legit. I can't imagine all the ways the electrical measurements might be mistaken, but a video of "look, this stuff hovers" sounds hard to mess up.
Got the video working at last (found a version of it on twitter), now I think its an update against the supercondutor. I have played with bits of metal touching magnets before, and they often sort of "spring up" on one end, or form slightly rigid structures. The video looks just like that, not like its levitating at all.
Other minor point. Their competing interests and data statements follow the Nature template, so that it very likely where it has been submitted. If the template had suggested submission to anything other than a high impact journal (Nature, Science) that would indicate some kind of problem.
"Sometimes, rocks just get hot."
This looks like legit levitation to me, with the stability forbidden by Earnshaw.
The rocks comic is funny, although its not a great example. If the rock is in the glare of the hot middle eastern sun it should be heating up despite being hotter than the surrounding air. The unimpressed people have probably seen rocks out in the sun before. "Sometimes rocks get hot, for example if they are exposed to sun light". Show me a rock that gets hot in the shade.
Yes, that is the video I found on twitter.
You could be right and it is levitation, but I had a thing called a "magnetic sculpture" as a child, and to me this video just doesn't look any different from how the metal rectangles in that toy stood on the magnet, usually at some preferred angle. Google "Magnetic sculpture" to get a lot of pictures of things like this:
On the other had, I have also seen the demonstration where an actual superconductor is lifted out of a bath of liquid nitrogen with some tool, then put floating (maybe also spinning) above the magnet. I thought that looked quite different, although all the liquid nitrogen "smokyness" could have just been adding so much cool that I was more easily impressed.
I am not seeing the relevance of Earnshaw. I thought that a superconductor floating in a magnetic field was distinct from one magnet pushing on an induced magnet. My vague understanding is that the magnetic field lines got "locked" inside the superconductor and that this was indeed stable (flux pinning is the term I think). I mean, I have seen countless demonstrations with cold superconductors and it seemed pretty stable, you could poke it to make it spin, and the poke wouldn't make it immediately collapse or fly away.
From the post: