Why scientists are so skeptical of the LK-99 room temperature ambient pressure superconductor
hi everyone welcome back to the channel so the internet is absolutely ablaze with this new potential discovery of a room temperature ambient pressure superconductor reported by one South Korean group but there's two papers that were released on the archive in July 22. since then basically there's been a huge number of news reports going on about how this thing could be a novel superconductor the consequences in terms of the new technologies things like superconducting stocks in Korea have been going through the roof in the New York Times there's been a new report this morning about how LK 99 is the new ambient superconductor of the summer and of course on Twitter there's been like all kinds of people weighing in about whether this is a new superconductor or not there's even been a twitch Channel which has been live streaming their experiment in replicating this this new LK 99 synthesizing it and then seeing whether they're superconductivity or not of course there's been all kinds of weird memes and things like that with fake reports of people verifying LK 99 this one is a supposed verification with basically a coin and a piece of fishing line memes about how this is the new chat GPT people anxiously waiting for new results on verifications and of course now everybody is an absolute superconductor expert right this in the scientific Community has been met with quite a lot of skepticism so this is a very early tweet that Sankar das Sarma made just about two or three days after the initial papers were put on the archive and already at this point people were skeptical if I just read out the Tweet he basically says that he's a another claim of room temperature superconductivity and levitation by another relatively unknown group with limited background in superconductivity in fact they make two bold claims in one evening obviously this is unlikely but the boldness is breathtaking I really like the way that he phrases this given this kind of backdrop I just what I want to do today in this video is just to give you a little bit of a sense of why the scientific Community is skeptical about it and basically let's see whether this we really have any hope that this will be really the Breakthrough that it promises to be okay the thing about this paper is that apart from the kind of the weird sort of writing there's all kinds of peripheral things which raises a few red flags even before you really start to delve into the paper right if you look at the lead researchers in the paper they come from this place called Qcentre in Korea but actually if you go to the website you can't actually get there anymore I don't know it's being shut down it's a bit mysterious in itself oh yeah it could be hacked with the intense pressure yeah it could be anything right but so about a week ago there was a another the video by Dave Jones from EEVblog I don't know you guys might be familiar with it at this point when he made this video this website was still up right and what you can gather from this website is that it's some kind of startup or some kind of commercial company rather than a research institution or a university and basically what Dave does in this particular video is to debunk a particular demonstration of this material which I think that this company is basically trying to sell you know this is basically their product and the video involves basically a piece of this material hanging from some fishing line and then they get a different magnet and then they like oscillate this magnet near this piece when I saw this video for the first time I also thought it's a bit weird I didn't really know what to to make of it actually is this supposed to show superconductivity or something maybe navigation yeah it's definitely yeah it's not really levitating is it it's like a string so it's yeah exactly but basically what Dave does in his video is that he basically replicates the same kind of experiment with a piece of copper and then this silver thing here is some magnet it's a weird shape but it's basically just the magnet and basically you can do the same thing and he just says this is just Lenz's law like you learn in high school it debunks that part well it's a bit mysterious what that demonstration was supposed to show but anyway the website's taken down regardless another weird kind of thing which people have already talked about a bit is that apparently the reason why there's these two papers is that this last author on the three author paper actually submitted it without the permission of the other two authors that's also another very weird circumstance which normally does not happen and presumably they knew about this because these two papers appeared on the archive kind of at the same time right so they probably knew that this guy was going to submit or something and then then they made sure that they also had their version up on the archive like on the same day so weird circumstances another weird thing is that they've had this material since 1999 this is what the 99 stands for in the name of the material they've had 20 years to basically perfect this material and investigate it and I'm sure it's not you know they just turned around this year and then figured out that it's you know a superconductor you know they've been playing around with this for for probably decades and considering this thing is a fairly easily manufactured material and people are just like doing this in real time on Twitch manufacturing this stuff and actually measuring its properties it's a bit weird that all this is coming out right now another reason why people are very skeptical about this is that there's been lots of room temperature superconductivity claims in the past and one particularly notorious case was this case by Range Dias back in 2020 he along with his team claimed that there was a material that possessed room temperature superconductivity obviously this paper as you can see here has been retracted now this came to be retracted because this guy Hirsch as famous from the Hirsch index the same guy he actually went after this group to show that basically there's something wrong with their results and in the end basically they were forced to retract their results but what's interesting is that even in this retracted paper their claims are not even as profound as basically what's being planned right now with this LK 99 right so if you look at the claims there it's temperatures of around 15 degrees Celsius that's slightly like a cold room and 267 gigapascals that's 10 000 times the pressure of ambient pressure right even these well we now believe to be faked results are actually quite modest compared to the results that are being claimed right now now that doesn't really mean anything really it but this really would be such a massive advance in comparison to what's available out there at the moment that's basically some kind of peripheral information that you just want to have in your mind just incidentally this yes guy also published another paper just earlier this year also of room temperature superconductivity again at again very high pressures right so this was accepted into nature presumably people looking at this also with quite an eye of skepticism but what's interesting even to look at the results from this retracted article is that there's some key signals of superconductivity if you're going to claim room temperature superconductivity then there are some sort of key things that you probably need in order to get it through to Nature and one of the key things is of course measuring zero resistance and even in this retracted article there is like this kind of plot here on the left where you see the resistance on the vertical axis and the temperature on the horizontal axis is and basically at some temperature it collapses to zero this is the classic Hallmark of superconductivity this is what honest saw back in 1911 with Mercury and this is still basically the classic signal that you really want to see you look at the results of of the paper it's just weird there is a plot like this this is in the sixth author paper so there's a plot of the resistivity against the temperature and indeed there is this drop that happens at 110 degrees Celsius not Kelvin but Celsius so this is like above boiling point of water but it doesn't really drop to zero right and it drops to some value which is it looks like about Point yeah 0.2 times 10 to the minus 2 ohm centimeters and so if you compare this to the resistivity of say copper this is like way higher right it's way higher it's resistivity of copper is 10 to the minus six in the same units right so this is is like 10 to the minus 3 versus this is 10 to the minus 6. if you just look at that you'd say yeah it's not really of course this later on goes down to smaller values but the scale is so big you can't really see what value this is really going to it's looking at something on a huge scale when you really want to see the small values right so that's a weird aspect of this really can't make heads or tails about it from the three author paper they don't have this classic resistance versus temperature plot or resistivity but they do have the one graph that they do show about the resistivity is this one where basically they show essentially at one particular temperature I presume of the voltage versus the current and then so from that you can work out the resistance and apparently from this larger plot they work out the smaller plot and I assume they do something like this and this is just my naive first year physics kind of method here but if you work out based the resistance of this because V equals IR right so resistance is V divided by I okay so you for example take one of these points here let's say it's about 0.1 micro volts let's say roughly
and this is 25 milliamps okay and so that will give you a resistance of about 10 to the minus 6 ohms okay and now to convert this into resistivity we need to multiply by the dimensional Factor like how big this sample is now again they don't really tell you exactly the sample size in that paper but in the sixth author paper they do taking the sample to be this Dimension and then calculating this A/L you get a resistivity of something like 10 to the minus 7 ohms centimeters okay now that is not really the same value that you you get in this graph right that you're getting something like 10 to the minus more 10 right so there's three orders of magnitude shoot missing unless I've done something stupid here you can tell me in the comments if this was all wrong but I'm not sure even how they can get these values of the resistivity okay obviously people have been trying to replicate these results and so far as for the resistance estimate I think this is the closest that people have come this is a very quick results coming from Southeast University that came out on the 2nd of August and they basically managed to measure a zero resistance but they could not do it at room temperature they need to go down to something like 110 Kelvin in order to see the resistance dropping to zero so basically the graph on the left here is the results in at some temperature around 110 the resistance basically goes to somewhere in the noise right but even this is being criticized quite a lot because this graph doesn't really have the classic shape of superconductivity what you'd expect so if you replay that same graph on a linear scale then it has this kind of more like curved dependence not like this sudden drop and generally phase transitions have an extremely sudden drop that goes to zero because it's like when ice turns into water it's a very sharp transition it's not like ice turns into water roughly in the range of -20 to 20. it exactly at zero is the phase transition point and phase transitions tend to have this very sharp behavior and the only sharp behavior that you see here is around here at about 230 Kelvin but this clearly looks like some kind of experimental artifact so going back to dasama's tweets here he's very scaling of these results that are coming out from Southeast University in inverted commas he says physics being presented in these unreferied preprints is a travesty the original paper has no obvious superconducting transition and the T < TC resistivity is a hundred times that of copper original so known as Southeast also has no transition just instrumental artifacts that's this sort of weird drop that you're seeing at 200 and odd Kelvin what is the goal here no one can fool nature very scathing of basically both of these reports right now onto the Meissner effect this effect of the superconductor kind of floating is one of the classic signals of superconductivity it's the effect that superconductors can expel all magnetic fields from within them and so this is why you have this levitation kind of effect right there's been also another follow-up video just this morning posted on the New York Times and they have basically a similar type of video again it's sort of floating but not entirely floating with one Edge on the side in terms of replication maybe the closest to any kind of replication has come from another Chinese group from the Hangzhou University of Science and Technology and they posted their video on BiliBili and they showed my tiny fragments of this stuff again showing this semi-levitation kind of effect right but the thing with this kind of levitation effect is that and this is the criticism that a lot of people are pointing out is that basic basically this effect is diamagnetism and diamagnetism basically means that it's a material that follows the magnetic field in the opposite way right a lot of materials that we're familiar with like iron are usually paramagnets right so your fridge magnet that you stick on your fridge if you put it on there the reason why it sticks is because the fridge door is made of some material including iron and iron is a ferromagnet and basically it will point it's magnetic field in the same direction as the applied magnetic field right so if there's a North Pole here on the magnet then the paramagnet Will Follow That magnetic field it will have a South Pole close to it and hence it will attract and so this is why fridge magnets stick to the door of your fridge right now diamagnets are the opposite so the magnetic fields that's induced are in the opposite direction right so the North Pole induces another North Pole near it and so it repels and so this is why diamagnetic materials can repel now there's this famous experiment by Andre Geim Ignobel Prize winner and Nobel Prize winner you've got the Ignobel prize for levitating a frog in a strong magnetic field and you can do this because basically frogs are full of water and so if you have a strong enough magnet you can levitate a frog but there's other materials like this which have quite a strong diamagnetic season for example this pyrolytic graphite is a material with particularly strong diamagnetism and so if you put such a material on the magnet it floats right this is not a superconductor this is just a regular diamagnetic material yes it's a relatively strong material it's a strong kind of diamagnet however it's it absolutely floats right superconductor of course also floats it has a much stronger effect than this but the fact that it floats is not a hundred percent signal that it's a superconductor and so this is why people have been saying that perhaps this material is just simply just a regular diamagnet another thing that people have been going on about is theoretical verifications of basically superconductivity in these materials one of the first papers that came out came from the Sinead Griffin from Lawrence Berkeley National Laboratory and basically in this particular work what they showed is that there's a kind of a flat band in these types of materials now possibly because she tweeted this along with a mic drop GIF of Barack Obama people thought that this is absolute smoking gun evidence that this really shows that LK 99 is a room temperature superconductor right and there's lots of tweets about how from this result quote insanely bullish for Humanity but in fact these types of results really only show partial information about how it might be plausible that superconductivity might exist in these materials and the main result it really is these calculator stations where they where they calculate the band structure and basically what is found in this paper are like two bands which are very close to the Fermi levels separated from the other bands by 130 meV and so why flat bands are important is because basically if you've got very energetic electrons which basically means that the bands are not flat then it's harder to combine them into this Cooper pair so that this kind of condensation effect can happen right in the flat band case if the electrons don't have so much energy just a little bit of attractive force can bind them together and then you can form this pair and then you can form the superconductor and so this is why flat bands are very interesting in terms of superconductive materials because this is one way that you can form these pairs so that you can get your superconductor in the first place but just showing flat and isn't really the end of the story that it just makes it plausible that you might get superconductivity but you really can't take these as just like some kind of smoking gun mic drop proof that LK 99 is going to be a superconductor further calculations would need to be done in order to basically prove this okay so firstly what do you guys think so even though why are everybody giving you that so much attention then that's what I don't really because even my first reaction when Valentin posted that thing was like okay there goes another one of those claims that's what I just said and that was it I didn't really follow it so much I didn't I wasn't really I don't know why yeah I think it just because must be a combination of people just be interesting it's a bold claim maybe a lot of people want it to be true because it would be a remarkable breakthrough absolutely yeah if it's true people say that it's a Nobel Prize stuff like that but it probably it really probably will be right right it's that amazing it's that much of a bold claim yes but the boldness is breathtaking besides that one paper has any other person said something else yeah there's been I think there's been about eight papers or so but just going through them you can go on Wikipedia and then there's like a running table of new papers that are coming out on related topics and I believe they're all actually seen this type of paper this density functional paper and they all have quite similar results actually so they all find this flat bands and so I think I'm not sure if there's much variety actually in the theory there's a little bit more variety in the experiments actually experiment wise nobody has ever besides the Chinese who's tried and fell yeah again there's I don't know maybe 10 experimental groups which are trying you can again look on Wikipedia because it's just it'll be just different tomorrow it'll be like another five tomorrow so yeah but in terms of the main ones as of today I think the ones with actual results that you can actually have a look at I think it's like the maybe three Chinese groups there's an Indian group but the other ones they say they have some results but it's hard to find actual information yeah this LK 99 has been around since right I thought maybe the properties of this material should have been well understood very well before now to say whether this can happen or not I think on the attention they adopted with copper or something so I think they were working like a variation of this material the properties should have been well known such that even if they tweaked it you should be able to immediately say yes or no that's what I that's what I'm trying to get at not necessarily but it looks like it's not yeah I agree with you it's just a weird thing about it because it's clear that they're aiming for superconductivity right yeah because they've been playing with this material for 20 years and I think this has been their aim for the whole time right yeah this is their pattern from three years ago it's definitely it's in the title like you can see that's what they're aiming for so so why this very scratchy results and yeah why is it so unclear like they had 20 years to look at this so I don't understand that story at all yeah I don't think only because like I said when I first saw it when I first saw the post I was like here goes another one of those fairy tales yeah but if I sitting here and thinking if LK 99 has been around for some time each property should have well known such that even if you tweak it a little people should we tell you okay this is what I should expect it's like it's not like that I don't know yeah and also I think it depends upon the sample as well right like so I think different samples for different properties and okay so it's I don't know pretty unpredictable stuff maybe theories to the risk here for this one actually huh yeah I think theories in this field to the rescue you can only do experience no no I agree with you the experiments have the final say on this right but at least the theory should be able to lead the way to make some interpretation about what is going on otherwise everybody will be still scratching their head because it all boils down to whether are they going to replicate what these people did or I mean for experiments either to replicate what these people did or to come out body and say okay this material can never be this or can never have this effect we can always wait for like very advanced molecular simulations but but like experimentally they find to not agreement with you okay so I think I would say that so the the problem with doing this kind of thing is these are strongly correlated materials right and this cuprate superconductivity which I think people had a lot of trouble in creating models and understanding that you have to solve these very large spin models which are notoriously difficult to solve right and it's not just like a band structure problem band structure is the first step then now you've got this strongly correlated materials that you need to solve which is like numerically like very hard and then they have to prove it so I think it's it's just you see it in experimentally you don't I think yeah oh okay in theory can provide a few sort of indications but you know it might be hard so debunking this might take some time then but this stuff is really easy to make so as long as experimentally okay people already made it right in a few days okay now they're just going to kind of make it better or cleaner or and basically everybody in the world makes it even people in the garages and nobody finds it and that's it that's the end of the story so from this equal mechanics perspective they claim that in this particular material the electrons are able to pair at room temperature and naturally yes okay yes that's a good claim yeah I think I didn't go into so much the mechanism but in the second paper they claim some mechanisms of why this might happen and basically what they say is that there's some kind of by replacing the lead atoms with the copper atoms there's some like kind of natural pressure that builds up in the material which makes instead of applying external pressure you have some internal pressure which kind of results in the same kind of effect but having said that I've also seen again I think the best armor Twitter thread saying that a lot of this basically explanation is absolute nonsense it nobody can really understand basically this mechanism as they explain it yeah they are getting a lot of scientists it is positive or negative both yeah like it is like flow or that is not supported by this so well it's a good way to get citations I think that even though I've presented this pretty skeptically ultimately there's still a chance that people can still find superconductors in in some weird material and it doesn't matter where you're from it doesn't matter you don't have to be from a great big university I mean there's no reason why it doesn't exist and this is why I think people are you know looking at this uh seriously but with a nice skepticism this is just how science works if you enjoyed that and we'll see you for the next one
2023-08-13 18:02
