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I got my PhD studying band structure of high-tc superconductors (experimentalist, ARPES). These Cu d-d interactions right at the fermi energy give me huge hope.
by bluecoconut 3y ago
I got my PhD studying band structure of high-tc superconductors (experimentalist, ARPES). These Cu d-d interactions right at the fermi energy give me huge hope. Feels very familiar to other superconductors (re: all the cuprates). (Note: I specifically worked in a lab that was measuring a lot of the d-wave character / gap-energies of various superconductors)
All in all, I'm now much more bullish on LK-99 being real superconductivity after seeing multiple different labs compute similar band structures. The video of multiple directions of magnet showing some levitation also inspires a lot of hope.
- SamPatt 3y agoThanks for your input. What would you need to see to say "I am 100% convinced this is / isn't real"? And how long would you expect it will be before that occurs?
- RandomBK 3y agoI'm not a scientist, but personally I expect I'll have two "wow, this is really happening" moments: (1) When there's peer-reviewed replication from a group of reputable labs. (2) When I see the classic superconductor-on-magnetic-track demo, but without liquid nitrogen.
- fragmede 3y agohttps://nitter.net/lereguy/status/1686363900651151360 https://nitter.net/lereguy/status/1686363900651151360 is no https://www.youtube.com/watch?v=zPqEEZa2Gis https://www.youtube.com/watch?v=zPqEEZa2Gis but it's on the way there!
- DeIonizedPlasma 3y agoThe nitter video could literally be a piece of iron, even a ferromagnetic object will turn like that under the presence of a magnet. It certainly isn't proof that the thing they have there is NOT a superconductor, but you can't use that video as evidence of anything.
- cthalupa 3y agoIron and ferromagnetic objects would not react that way. The key to this showing diamagnetism is the fact that the same points are repelled in the same way regardless of the orientation of the magnet. If it was ferromagnetic, you could have it stand up on it's tip in one polarity and stand up on another portion of the object in the other polarity, but you couldn't make it stand up on it's tip both times.
- bluecoconut 3y agoI'd probably approach 90% confidence with ~2-3 different measurements from different labs showing similar stories. Select from the grab bag of possible experiments that could all collaborate and provide consistency in their stories: specifically things like measuring the critical current, critical magnetic field, high quality electrical resistance in various ways (lots of transport), STM measurements of gaps, ARPES measurements of gaps, XRD showing crystal structures are what we expect that matches the DFT, a study on the domain sizes/effects (since this is relying on a substition at the right place, necessarily I suspect that there will be domain effects / "doping" style things... so how those play out in terms of purity and quality of results will be interesting). There will be a lot to study and characterize, and every extra measurement that is consistent rapidly increases that confidence. I'd say I'd get to "100%" (as close as someone could be) after ~10-20 papers across many different labs and measurements. I'd hope we'd get there in ~3-6 months. What I'm actually even slightly more excited about is "what comes next" -- not the market part, but the "fast follow science". For instance, in the few years after LCBO and LSCO were found (TC~30K) we quickly found YBCO and BSCCO (Tc~130K). I would expect that we'll find a whole class of these materials with substitution tricks that possibly work, and there will be a whole slew of options for "going to market" with the technology. The door this opens is what is more exciting than the specifics of LK-99 itself in my opinion. Estimating times, after the fast follow science (0.5-2 years optimistically?) we will hopefully have the actual "we're all convinced this is real, and the technology can start to be applied in real devices". Specifically, after everyone is pretty clear on a lot of the material properties and ways to reproducibly make high-quality crystals, so consistency is clear on measurements... then begins the cycles on how to manufacture high enough quality material at scale that it can actually be applied. (specifically, these materials (assuming they're like YCBO/BSCCO) are superconducting crystals that have grains, alignment issues, are physically brittle, have homogeneity issues, etc.) While each solvable, these are all real engineering and material challenges that increase cost to manufacture, and all of this will probably take time before we suddenly get wide-scale products that use this (this is all assuming it's real, haha, there's still plenty of reason to be skeptical).
- SamPatt 3y agoThanks for your thoughts!
- JKCalhoun 3y agoWaiting for Applied Science (the YouTuber) to make some in his lab.
- eco 3y agoI think he might be working on it. On Twitter he teased a homemade device for making very fine powder for, say, superconductors. Here's his video of making YBCO for anyone that hasn't seen it: https://www.youtube.com/watch?v=sLFaa6RPJIU https://www.youtube.com/watch?v=sLFaa6RPJIU
- anigbrowl 3y agoSo happy to hear this. I've been hoping for some sort of breakthrough ever since I first encountered footage of magnets falling through Cu tubes at an extremely leisurely pace.
- redrobein 3y agoAny conductive material for the tube will have a similar effect. It isn't specific to copper. The moving magnet induces a current in the tube which in turn creates the magnetic field that interacts with the magnet.
- soligern 3y agoEddy currents
- sjcsjc 3y ago“Eddies,” said Ford, “in the space-time continuum.” “Ah,” nodded Arthur, “is he? Is he?”
- TheSpiceIsLife 3y agoNot any conductive material, obviously won’t work won’t work, nor magnetic steel / stainless steel alloys.
- TheSpiceIsLife 3y agoI meant: obviously iron won’t work.
- fodkodrasz 3y agoCould you elaborate why iron pipes wouldn't work?
- andrewflnr 3y ago
- jpmattia 3y ago> These Cu d-d interactions right at the fermi energy give me huge hope. Feels very familiar to other superconductors (re: all the cuprates). As someone who is versed in semiconductor band structures but not superconductor band structures: What is it about Cu d-d interactions that causes the superconductivity? Degenerate energies in semiconductors don't give rise to electron pairing, so I'm a bit out to sea with the proposed mechanism here.
- bluecoconut 3y agoTo be honest, this is a hunch thing more than a I can teach and explain it thing. To me it's just "a lot of the same stories" that are told about cuprates, and less of a "I can explain the mechanism". Roughly, one of the "properties" that shows up with these materials is that the 3d orbitals of coper atoms are involved in forming the bands near the fermi level. Couple that with the fun story of Cu electron configuration being [Ar] 3d^10 4s^1, which suggests that spin-effects are "at play" with these electrons near their filling levels. Combine that with the spin-character properties of cuprate paring (eg. s-wave vs. d-wave superconductors, (d-wave for BSCCO for instance)). All together it lends itself to a nice spin-orbit coupled band "setup" at the fermi energy that I have a hunch somehow backs the underlying mechanism of these d-wave superconductors. Fully admit, there's some leaps there in the raw logic -- if I could fully explain it I probably would still be in the field, haha. I'll note: I've been out of the field for ~8 years, but a quick google search led to some more recent papers [1][2] working through plausible explanations based on some of these copper d orbital shenanigans. [1] https://www.scirp.org/journal/paperinformation.aspx?paperid=89967 https://www.scirp.org/journal/paperinformation.aspx?paperid=... [2] https://arxiv.org/abs/2105.11664 https://arxiv.org/abs/2105.11664 (d-p, but includes the Cu d-orbital and also specifically states "We also show that the effect of the nearest-neighbor d-d Coulomb interaction Vdd is actually quite important for the stability of superconductivity and phase competition.")
- jpmattia 3y ago> To me it's just "a lot of the same stories" that are told about cuprates, and less of a "I can explain the mechanism". Fair enough, and thanks for the readout. I realized after posting I essentially demanded an explanation as to why the cuprates are high-Tc, which is probably its own Nobel prize.
- Baeocystin 3y agoSerious question- I saw the original video, where once they stopped waving the magnet around and held it near the sheet of LK-99, it looked to me like it stayed at a specific standoff distance, with no decay. Assuming no videographic trickery, what else could it be, other than the Meissner effect?
- oceanghost 3y agoA diamagnetic material. "In simple terms, diamagnetic materials are substances that are usually repelled by a magnetic field. Electrons in an atom revolve around the nucleus, and thus possess orbital angular momentum. The resultant magnetic momentum in an atom of the diamagnetic material is zero."
- Baeocystin 3y agoAm I correct in my understanding that being capable of self-levitation would be an unusually strong example of the diamagnetic effect?
- lucubratory 3y agoYes, if this material is diamagnetic without being a superconductor it is by far the strongest such material we've ever found. 15x stronger than pyrolitic graphite.
- tavavex 3y agoFrom what I heard, it would. This kind of diamagnetism would be strong enough to be potentially interesting in other applications and research, if it turns out not to be a superconductor.
- nine_k 3y agoWould still be useful for maglev, I assume?
- ajnin 3y ago
- jurgenaut23 3y agoBeyond the raw scientific excitement, can you explain how this would affect mankind (positively and, of course, perhaps negatively)?
- xvector 3y agoImpact of superconductors: https://threadreaderapp.com/thread/1685088625187495936.html https://threadreaderapp.com/thread/1685088625187495936.html
- itsoktocry 3y ago"1970: Superconducting trains to go from New York to LA in 20 minutes!" 50+ years later the US has how many high speed trains, of any kind?
- kuschku 3y agoWell, Shanghai has some, Japan is building some, and if this discovery is real, Germany might as well revive their Transrapid project (which built the shanghai one).
- marcosdumay 3y agoI guess that's partially missing the point. The main benefit of a superconducting maglev is that it's cheaper to build than a on-rails high-speed train. Specially on problematic terrain (what I understand includes every possible East/West route on the US).
- irthomasthomas 3y agoI think we're being trolled. Or trawled. Not sure which, yet. But the mention of Salvatore Cezar Pais in the patent should be enough to put this to bed for serious folks. https://news.ycombinator.com/item?id=36967333 https://news.ycombinator.com/item?id=36967333 In case you aren't familiar with the man's work, here are some highlights of his discoveries over the last decade: Conditional possibility of spacecraft propulsion at superluminal speeds High frequency gravitational waves-induced propulsion Piezoelectricity-induced room temperature superconductor Craft using an inertial mass reduction device On the Existence of the Superforce–the possible fundamental Force of Unification https://scholar.google.com/scholar?hl=en&as_sdt=7%2C39&q=Salvatore+Cezar+Pais&btnG= https://scholar.google.com/scholar?hl=en&as_sdt=7%2C39&q=Sal... I can't wait for my cheap antigrav FTL iron man suit to arrive next year.
- dcgudeman 3y agoI wonder why more people aren't talking about this
- nwoli 3y agoWould be pretty funny if this guy actually published a breakthrough that worked all of a sudden
- varjag 3y agoI wouldn't read too much into this. You have to address prior art when it is found in patent examination as a part of application process, no matter how bogus it is.
- 3y ago
- weinzierl 3y agoThis is probably a very stupid question, but why is simply measuring resistance not enough to conclusively prove that it is a superconductor. I mean, isn't zero resistance the defining property?
- vrotaru 3y agoWell, I guess, that are islands of superconductivity and normal conductivity in the same sample. This gives a low resistance and diamagnetism which is used as proxy to real superconductivity. I may be wrong though.
- OJFord 3y agoI think if it was actually zero it would be? The issue I think is impurity/defects in the manufactured samples, so there's non-superconducting bits in addition to the allegedly superconducting bits.
- rvnx 3y agoJust guessing: I would say not enough because the sample is extremely small and there is chance that the electrons jump from each sides of the probes, skipping the sample ? (like a short-circuit) + the fact that the probes themselves are not superconductor, so there is a natural accepted tolerance in the measures (claimed to be due to the probes)
- mianos 3y agoIf the video is to be believed, the samples shown are huge compared to a, trivial to make, pulled or cut platinum wire probe. You could just put it on a plate in an SPM and measure it. So many questions. I assume this is all possible but they are focussing on one thing at a time to duplicate the results, if possible.
- baq 3y agoMeasuring zero resistance turns out to be quite difficult because your measuring apparatus tends to have some resistance in itself. Perhaps heating it up while it levitates would be a better idea. Put the magnet in an oven together with the sample and bake?
- MrBuddyCasino 3y agoThis is probably the most stupid question to ask, but while were are still trying to confirm superconductivity instead of understanding its precise mechanism of operation, why the focus on levitation on band structure to confirm the news instead of just "yep this chunk has actually zero Ohms"?
- pjc50 3y ago"zero ohms" is very tricky to measure because of contact resistance: your probes aren't superconducting, and the thin contact surface between your probes and the metal itself isn't superconducting either. Whereas the Meissner effect is unique to superconductors. It just has to be distinguished from diamagnetism, and there are materials which are strongly diamagnetic but not superconductors.
- cyberax 3y agoBuild a loop out of a superconductor, induce a current in it, and then measure the resulting magnetic field after a couple of minutes. If the field is still there, then you have a superconductor.
- jacquesm 3y agoBecause the levitation thing works with tiny fragments too whereas the 'zero Ohms' measurement only works when you have enough of it to form a long enough wire of it that you could tell the difference between 0 and 0.000001. Measuring very small resistances is usually done by letting a known current run through them and then to measure the voltage across the sample using known resistance leads. For a superconductor that has a tiny available sample which is already conductive even if it is not superconducting is fraught with error and may well give you the wrong answer due to a tiny measuring error. But the Meissner effect is a unique signature of a diamagnetic material and will provide you some evidence even if the sample is tiny. So I understand why they have not yet resorted to other measurements, if there is no Meissner effect you don't need to continue with the hard work of trying to make a wire (which may well be a serious challenge for this stuff, the yield will have to come up significantly before that's a real possibility). hth
- norturnn 3y agoAnother ARPES person! Totally agree with you, not only the density of states but the flatness of the d band at the Fermi level is extremely encouraging. The simulated results look good enough that even if they had come out first I think that they still would have prompted someone to synthesize this.