You absolutely can, and as you can see in this paper it is absolutely do-able to measure the resistance of these materials. They measure an insulator with something on the order of 10^6 ohm m. For reference, copper has a resistivity of ~ 10^(-8) ohm m, so there are about 14 orders of magnitude of difference. This does make the contact resistance pretty negligible in this case too.
There are measurement configurations that can be used to eliminate contact resistance (such as a van der Pauw measurement). Resistance, and electrical measurement in general, is the true proof - the Meissner effect is secondary and more confusing as, since this paper shows, a small ferromagnetic phase can give rise to the same effects.
You can't completely eliminate contact resistance, and all instruments have a noise floor, so electrical measurements don't constitute "true proof", they are an element of proof among others. The Meissner effect is perfect diamagnetism which can cause levitation and is not like ferromagnetism which only can allow a piece of material to stand up to align itself with field lines (and which is what we've seen so far).
Groups that typically do resistivity measurements on regularly measure low-temperature resistivities on conducting materials of ~ 10s of micro Ohm m. So if you're measuring in this range on a conducting material and hitting the noise floor with a SHARP drop, that's a pretty big indicator of superconductivity (assuming you haven't just broken your contacts which is a concern when cooling things down). I'm not so familiar with PPMS systems, but I imagine it has some built in auto-adjust on the sensitivities to where you can be pretty confident your noise floor is below these values.
What is complicating the interpretation here is the log scale (and lack of conversion to resistivity): It is amplifying the impression of the noise below what they call Tc, and making it harder to interpret the approach of the material to the transition point. The behaviour at the approach to Tc also doesn't really look like a metal, which should scale as propto T, or a semiconductor which should increase with decreasing temperature. Possibly a result of it being some horrible mixed phase ceramic.
Something that I find hard to understand is why there is superconductivity without cooper pairs; granted my understanding is related to more traditional superconductors and I'm not really very knowledgeable about the cutting edge high-Tc stuff.
Compared to recent controversial results claiming the exact same thing (actually, more restrictive than this claim), it's not insulting it is what you should expect. The recent situation with Dias this year[1] is now under investigation as a case of data fabrication and he didn't even claim to have ambient pressure.
Frankly there are too many details missing to trust them. They've fabricated a thin film but not characterized it. It is well known that the properties of a material change when you go from bulk to thin film with a big dependence on the thickness. They don't mention how the resistance of this thin film is measured - that's important for what artifacts you might expect to see in your measurements (van der Pauw vs Hall bar measurements are the standard but they don't mention using either). Without characterizing the thin film it's also difficult to know, chemically and structurally, what you are measuring. I don't see any data confirming the quality of the thin film. The way the data is presented is such that it can be misleading, showing I-V curves instead of resistance when you are really trying to say the resistance is what is changing. The first paper doesn't even mention the insulator-metal transition that is present in the second paper which is bizarre - this is important if you are also claiming a superconductor transition close by and you would expect some discussion of this behaviour.
All of these are things that, one would hope, will be picked up by the reviewers as low hanging fruit before even really delving into the detail of the theory they present.
Decades of experience alone should not be trusted. Anyone can make a mistake, and not all the authors can be present for every experiment.
Glad to see a realistic take on HN. Endlessly frustrating to see people be like "this will be replicated in days". Yeah, sure, let every other lab just drop what they're doing, order all the reagents on express, do a thorough characterization making sure they understand the impurities and crystal phase, then perform good airtight measurements in a couple days. Crystal growth always has complications many times outside of your control - the most minor of things can cause ridiculous problems.
Especially when they admit to having phase impurities, and it's not really clear how they've gone from bulk sample to measurement sample (are they really measuring just the superconductor or the impurity phase?). Needs addressing, especially when the Cu2S phase impurity seems to have a phase transition of it's own at or around 370K (suspiciously close to where some of their Tc measurements are).
Replication attempts don't give you an unambiguous signal, many things can go wrong.
If one lab hasn't succeeded in replicating the paper, does that mean the paper is wrong, or just that a necessary step wasn't documented clearly or followed correctly?
More labs trying to replicate give you more independent signals.
Although the experimental protocol had not been published, physicists in several countries attempted, and failed, to replicate the excess heat phenomenon. The first paper submitted to Nature reproducing excess heat, although it passed peer review, was rejected because most similar experiments were negative and there were no theories that could explain a positive result;[notes 2][42] this paper was later accepted for publication by the journal Fusion Technology. Nathan Lewis, professor of chemistry at the California Institute of Technology, led one of the most ambitious validation efforts, trying many variations on the experiment without success,[43] while CERN physicist Douglas R. O. Morrison said that "essentially all" attempts in Western Europe had failed.
My memory is fuzzy, but my recollection is that Pons & Fleischmann's non-discovery involved unclear "waste heat" measurements, and a setup that wasn't well described, making it difficult for other researchers to duplicate. That would seem to contrast with Sukbae Lee, Ji-Hoon Kim, and Young-Wan Kwon's work, where everything suggests they've provided a readily replicable description of the material and process, and the evidence (magnetic levitation) is going to be pretty obvious.
I mean being thorough will obviously take a long time, but if a decent number of research groups decide to drop what they're doing and attempt a replication I don't think it would take that long for one of them to at least partially succeed if the claim is true. That doesn't mean they're publishing a sister paper, but it might mean we see some tweets saying "my group synthesized LK-99 and we have reason to believe it may be a rtp superconductor"
I would only expect these kinds of posts from a throwaway account created very recently with a single post.
Anyone with a long HN history is more likely trying to karma farm and chase clout by spinning up some bullshit. Trying to establish themselves as an authority on a trending topic.
But because a throwaway account has no past or future, it is the purest form of communication.
It is entirely believable that a person with substantial trace on HN and ties in the field would rather create a throwaway than post such remark under his main account.
Then they would not out their identity by claiming to have worked with the author. That piece of information alone whittles their identity down to maybe 100 people. Out of 100 adjacent academics how many post on HN, with this style, and this specific level of knowledge in that specific subfield? They may as well have just made the account their irl name. Anonymity is not a realistic goal. Assuming a realistic poster means it's reasonable to suspect their earnestness.
You are frustrated and this makes you act in a deliberately obtuse manner.
There is a world of difference between "anyone who has worked with the guy" and "has worked with the guy + has hundreds of comments on HN identifying career track over the last few years". The former grants each suspect plausible deniability, while the latter pinpoints the true author.
> Anonymity is not a realistic goal.
It obviously is for a throwaway account. Time to reread the classic
i agree re. skepticism but all I'm saying about HT Kim is that he's a real scientist with real bona fides, which I think you could find by asking anyone in my specific subfield of condensed matter physics
i should also have mentioned that I do not personally know the extent of his knowledge about superconductivity, to my understanding he was an expert on the synthesis of phase change materials, particularly the metal insulator transition. in the 2nd paper he is cited for proposing the superconductivity mechanism based on mechanisms seen in the metal-insulator-transition, which I have not seen before as an SC mechanism
To me the biggest mystery is why they didn't make multiple samples and send them to a few places that could verify their claims immediately. I understand that the papers were published before they really wanted to but they've also apparently have had samples for awhile it sounds like?
So assuming it's not BS (and I doubt that it is) it would lead me to believe that making the material is difficult to get right? The video they've produced uses a sample that isn't particularly elegant, to be sure.
I guess it's all conjecture at this point and healthy skepticism is warranted. A press conference would be nice.
Skepticism is warranted, but apparently there's infighting in the group (only 3 people can be recipients of a Nobel Prize) and one jumped the gun to get his name out there. And also apparently fear of research espionage from the PRC (not as far-fetched as it sounds).
Man, fucking scientists dude, they need to get their heads on straight
If you're one of the 7 people who invented room temperature superconductivity, it's not going to matter who has the Nobel Prize. You can take a part time 7 figure consulting gig and be as famous as you want to boot
Most famous discovers of famous phenomena do not get 7 figure consulting gigs. Did any discoverers of high Tc superconductors, quantum hall, topological insulators, blue LEDs, graphene get rich? Not as far as I know.
i do not understand this either regarding the samples, usually(in my limited experience) synthesis groups have collaborators that specialize in transport or other types of measurements which I think would have added a bit of credibility, probably could have gotten a measurement of Tc, and just generally added a lot to the paper
That could very well have been their plan, they just got beat to the punch by the paper leak. Shrug. Probably won’t get the full story til next summer when Netflix inevitably does a C tier docu-drama series about it.
In the New Scientist interview HT Kim seemed to imply that he wouldn't help other researchers until his paper gets published. If the synthesis ends up being tricky this could take a while.
0.3 T is pretty insignificant for everyday use - you need some pretty big coils carrying around 10 A to produce that sort of field. For something like this, the benefit would be in just making wires out of it for driving currents without loss of power (no resistance, no heating). Think big bulky overhead wires - but it's all moot if the material isn't a superconductor.
In the first paper, they claim to measure zero resistance (on a scale of microvolts), but are very careful not to show full RvT curves - in the second paper, we can still see significant changes below Tc where they include more complete curves. How can the resistance change significantly in the superconducting (zero resistance) state? We can actually see significant noise in paper 1 fig. 1c in the ohmic state and it even appears to behave as an insulator at 0 field (increasing resistance with decreasing temperature), but a metal with applied field. There's something wrong with the measurement.
400 K is an odd choice for your superconducting temperature, and just so happens to be the top end of what an MPMS system can measure so is not completely random. Surely it makes sense to measure significantly above this with one of the oven attachments, verify these results with collaborators at other labs even.
10 Gauss is an extremely small field to use for a ZFC-FC measurement and again if their superconducting Tc is at or above 400K they need higher temperature data to show anything about the phase transition.
The claim that they have measured the density of states is completely unjustified - not even a citation. I don't know how you can believe that to be the case.
And in general the presentation both of the data and the paper itself is poor - if you just made a groundbreaking discovery like this, wouldn't you care?
> if you just made a groundbreaking discovery like this, wouldn't you care?
Hell no! If I had made a discovery of similar magnitude I would have done exactly what they’ve done: push out a rough preprint ASAP to reserve my Nobel prize, then take a deep breath, relax and take my time dotting ‘i’s and crossing ‘t’s for the real paper in Nature.
That doesn’t mean they’re correct, but there’s nothing inherently suspicious about the way this has unfolded.
Exactly, they have made a very big claim and made it very easy to replicate / falsify. It takes a few days to produce this stuff.
Their paper is weak on data / results.
This is exactly what you would do if your team genuinely believed you had discovered something monumental.
In poker terms they are "all in" and they want to get called.
That's why it is so interesting. If they had posted lots of extreme results but it needed $10m to replicate then I would be thinking "fraud". It would look like a bluff.
As I mentioned in my above post, they have really dodgy data. Ideally, with something like this, you would have collaborators to verify alongside you as joint co-authors. I think something people underestimate if how easy to replicate samples are - crystal growth is difficult, and impurities are important. It is unlikely anyone will produce exactly the same sample only something close based on the process they've given.
In realistic terms it seems they're grabbing for the prestige without the foundation of crossing their ts. Bad science like this shouldn't be encouraged. It's likely there's not very many groups growing the same material system so they have the time to spare. A paper like this wouldn't be on the arxiv at all if they were 100% sure because they would go straight for the nature publication and take the time to do more follow-up papers while they can.
Edit: to be clear as well, a lot of people are underestimating the time it takes to reproduce a growth even with a manuscript telling you how to do it. People always leave out steps and oversimplify. There is a lot of extra characterization that takes time to double check you have the right material that lines up with what they have here. Only the direct competitors actually already growing this material can do it in a few days.
