In short, they claim to have a room-temperature superconductor that works at ambient pressure (instead of only under a diamond anvil or the like). Or rather, they claim to have a superconductor that works all the way up to 127 C!
The papers don’t appear to be complete bunk, though, so the attitude should probably be one of skepticism rather than dismissal. One nice thing about it is that the material is easy to synthesize, and the claims easy to verify. This isn’t something that requires specialized equipment that only exists in one lab, or where the effect is so tiny that you never really know whether it’s noise or not.
For instance, they demonstrate levitation over a magnet, which is a property of all superconductors–and trivial to see if it works or not.
So, don’t get your hopes up yet. And even if it can be reproduced, it is far from being a commercially viable material. But it will be interesting to see the followup, which should be fairly quick.
My initial reaction (to some knowledgeable colleagues):
Damn! After reading the first page of the Introduction, I was expecting to see room temperature SQUID data. Turns out they just used a conventional SQUID to measure magnetization.
I’m not sure any of the measurements shown on page 3 convince me. However, they do conclusively state:
“LK-99 is a gray-black color, as shown in Figure 3(b). It is the superconductor with the same color as typical superconductors.”
I’m not sure I’m convinced by any of the figures, especially since they don’t describe the experimental set up used for most of the figures. I am heartened that my speculation that they might be able to use atomic substitution in the lattice to produce the same effects as applying external pressure is being followed through on.
The “conclusively state” section is sarcastic, in case you didn’t catch it.
FWIW, there is a video out there purporting to be levitation of this material.
On the other hand, this group apparently had to withdraw claims of room temperature superconductivity made in 2020.
Wait and see is definitely advised.
ETA: it is a little known fact that the discovery of YBCO was prompted by Paul Chu’s work on superconductivity under pressure and his thoughts that such pressure could be accomplished by lattice substitutions of larger atoms.
The whole thread is interesting, I just posted that tweet in response…if you (generic SDMB you) work your way upstream you can read some ways it was be hugely beneficial.
Is there any intuitive explanation for why pressure encourages superconductivity? Seems clear that it plays a significant role. Not that anything about the theory of superconductivity is really intuitive, but I vaguely get Cooper pairs, at least.
The video, for those that don’t want to click through:
I’ll just note that that video does not show levitation: A corner of the chip is always in contact with the base. I mention this because, while stable levitation is a property of superconductors, it’s really easy to get any old ordinary magnet to almost-levitate with only a tiny bit of direct contact to stabilize it.
Which makes me pessimistic: Surely, if this material were what they claim it is, it wouldn’t have been hard to get actual levitation.
No, that paper from Rochester was from 2021. The Gigazine page refers to a 2020 paper from this group (but I haven’t found any other cites)
Since BCS superconductors depend inherently on electron-lattice interactions, its intuitive that changing the lattice dynamics would affect superconductivity. However, my understanding is there is no consensus (still) on the theoretical underpinnings of HTS (even YBCO). I’m not a theorist, though.
In rereading the Gigazine page (now there’s a highly respected scientific journal cite!), it is unclear whther they are stating that this group withdrew their claims or some other, earlier group withdrew claims.
From what I’ve read, it’s not uncommon to have this partial levitation effect in superconductors. Sure they could have faked it by embedding a tiny magnet in one corner of the sample, but they could have faked lots of other things, too.
Well, either it’ll be reproduced or not. It doesn’t seem like this will end up like cold fusion or whatever since the effects are so dramatic.
It’s hard to get a feel for the video. On the one hand, there doesn’t seem to be any condensation or other indications of cooling of the superconductor chip. On the other hand, at one point the chip falls flat on the magnet, then pops back up, which is strange.
However, my experience playing with levitation is always with the superconductor cooled as the base and the smaller magnet levitating above it. The usual indication that you aren’t dealing with two magnets is that when you poke the magnet it resists displacement because of flux pinning in the superconductor (in fact, once you have levitation achieved, you can flip the superconductor over to show the magnet “hanging” from the superconductor instead of “floating”). With magnets, any levitation tends to be unstable, where any disturbance causes flying apart or sticking together. My first question when someone said there was a video was “Did they poke it?”
But I have no intuition when it comes to a small superconductor levitating above a large magnetic surface. Is the behavior shown in the video consistent with a sample where the superconductivity is not uniform?
Seems reasonable enough. If the sample were impure or not consistently structured, such that only one part was actually superconductive, I’d think you’d get that kind of behavior. But I agree, it’s hard to judge.
In fact, there’s a theorem that any static arrangement of magnetic dipoles, electric charges, and/or gravitating masses is unstable. It’s not even difficult to prove.
(the catch, of course, that allows for superconductive levitation, as well as the normal cohesion of the atoms in matter, is that the charges/magnetic poles in those situations aren’t static.)
I don’t think that’s quite correct. Penetration and pinning of flux is necessary for stable levitation. If you try levitation using a Type I superconductor (most elemental superconductors like Pb or Al are Type I, and most require liquid He temperatures or lower), the magnet flux from the magnet does not penetrate while the exclusion of flux (Meissner effect) still creates a force on the magnet so the magnet is unstable in position and will “slide” off.
Type II superconductors exclude flux completely below a certain field strength, but above that limit, instead of returning to the normal state like Type I, they create spots of penetration, called fluxoids. These fluxoids are arranged in a regular lattice on the superconductor and it is energetically unfavorable to move them from where they are on the superconductor (pinning).
Of course, there is also flux penetration through grain boundaries in both Type I and II polycrystalline material, but it is trickier to engineer flux pinning at grain boundaries in Type I superconductors, so they are still very unstable in levitation.
However, because of the very low transition temperature of Type I superconductors, a simple tabletop demonstration is out of the question, so you’re not going to find many videos of people trying levitation using lead (Tc ~7 Kelvin).
From what I’ve heard, this was made in a fairly straightforward way from materials that are widely available. So it should be confirmed or denied fairly quickly.
I didn’t say that dynamic charges were a sufficient condition for stability, only necessary. Obviously it’s possible to create dynamic systems that are still unstable (in fact, magnetostatics, when you get right down to it, is just a special case of electrodynamics).
On the other hand, the process (if true) apparently isn’t completely reliable, given that they’re claiming that only parts of their specimen are superconducting.
My impression is that this is easy enough that a lot of labs will be trying to reproduce it. This isn’t an area I know anything about, but my friends have been talking about it. Anyway, I guess we’ll see.
If true, it may be very sensitive to the level of dopants in the sample, etc. And if not well controlled, it could be that for a large sample, there’s variation in the structure and it’s only superconducting for the part where the levels are just right.
Not too different than early semiconductor work, where it took a long time to get consistent results. But even if it’s inconsistent at first, they should be able to get working samples with enough tries. If the effect is real, that is.
