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Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

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Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#251

Post by adrian_b »

bandrami wrote: post #70
evancox100 wrote: post #63

Earlier quoted context omitted.

Not a superconductor expert, but resistance exponentially decreasing with temperature is not a normal phenomenon in most cases!

Most semiconductors have a thermal regime where that happens, it's just a relatively small regime, I thought?

Here the resistance decreases in the opposite direction, so it cannot be explained by changes in the concentration of free carriers, like in semiconductors.

In metals, the concentration of free carriers is constant and the resistance decreases towards lower temperatures because the mobility of the free carriers increases, i.e. there is less friction between them and the crystal lattice, because the vibrations of the latter have a smaller amplitude. However this does not lead to any exponential decrease of the resistance.

The weird current dependence on voltage and temperature that can be seen here is most likely caused by an inhomogeneous sample that is composed of many small domains with different electrical properties.

Moreover, the material may be anisotropic, so extra variability is added by the random orientations of the microcrystals that compose the ceramic sample.

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#252

Post by adrian_b »

evancox100 wrote: post #106
bandrami wrote: post #70

Earlier quoted context omitted.

Most semiconductors have a thermal regime where that happens, it's just a relatively small regime, I thought?

I should probably be fired for my prior answer because things like pn-junction diodes can definitely have an exponential-like dependence on temperature. In my head I was thinking of pure elements, like bulk metals. But there definitely could be more interesting things going on in the sample, like diode formation (internally or at the contacts) or weird doping profiles. That may be part of why it's hard to measure the…

Intrinsic semiconductors or the semiconductors that are lightly doped with impurities have temperature ranges where the concentration of the free charge carriers increases exponentially with increasing temperature, like in the NTC (negative temperature coefficient) thermistors.

This causes a decrease in resistance towards higher temperatures, so it has nothing to do with any explanation for a decrease in resistance towards lower temperatures.

The diodes have increasing inverse currents towards higher temperatures, which also has nothing to do with any explanation for increasing currents towards lower temperatures.

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#253

Post by rsfern »

archon1410 wrote: post #193
rsfern wrote: post #109

Earlier quoted context omitted.

The SI unit is just “kelvin” because it’s an absolute scale. Usually “degrees” is only used with Celsius and Fahrenheit scales because they are relative. Not sure about Rankine… https://www.nist.gov/si-redefinition/kelvin-introduction

> zero on the Rankine scale is absolute zero, but a temperature difference of one Rankine degree (°R or °Ra) is defined as equal to one Fahrenheit degree But Rankine is an absolute scale. "By analogy with the SI unit, the kelvin, some authors term the unit Rankine, omitting the degree symbol." https://en.wikipedia.org/wiki/Rankine_scale

Ah, interesting - this NIST page uses °R, which is at odds with the explanation in the other page on Kelvin (which doesn’t mention Rankine). I’m not sure if that’s because there’s a strong convention to use the degree symbol with Rankine or if there’s an additional reason not mentioned by the Kelvin page

https://www.nist.gov/pml/special-publication-811/nist-guide-...

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#254

Post by vinnyvichy »

_0ffh wrote: post #240
cthalupa wrote: post #146

Earlier quoted context omitted.

> I'm actually surprised by the sheer lack of people commenting in the more-or-less-perma-LK-99 threads who show skepticism of the results. There's plenty of people that are skeptical and making it a point to tell everyone they are skeptical. There's plenty of people that are skeptical that are still engaging on the possibility of it being real because it is interesting to do so. There are plenty of people discussing…

Ha, I've been talking about the same topic with an experimental physics professor friend of mine. He was just not interested at all, like "I've seen stuff like that so many times before, I'm not interested at this point. I may look at it when there's a publication in a serious journal." while I was like "Hey it's popcorn time, this is a fun ride, whatever the outcome!". =)

Speaking as an academic, I really hope they don't ever publish in a serious journal even if it turns out to replicate. Did your friend take Ranga Dias seriously because that was published in Nature? I understand there's a lot of noise, but one of the things one learns is to cut out noise without having to rely on journal brand

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#255

Post by SanderNL »

jcranmer wrote: post #74
tomohelix wrote: post #30

Summary of events so far: The claim: Room temp (~300K) superconductor exists and we got it! The replication attempts: The production method is so poorly documented only a fraction of the samples being made shows any interesting properties. And among those interesting ones, results varies. Very few, if any, attempt actually completely shows the entire spectrum of properties and behaviors of a true superconductor at ro…

> Worst case scenario, we got another class of high temp (warmer than liquid nitrogen but cold enough that applications are limited) superconductor but nothing revolutionary since at this point, it is pretty conclusive that there is something interesting with LK-99. I don't think that's the worst case scenario. The worst case scenario is that there is actually nothing interesting with LK-99, and everything we've seen…

It's good to keep an open mind both ways, but "skepticism" without either interesting or convincing arguments is IMO just as useless.

We all know there is a good chance it turns out to be a dud. We all know cold fusion/emdrive/superluminal experiments turned out to be duds. We all know this.

I wonder what news do "skeptics" have to bring to the table. Nothing a skeptic has to say changes anything. We are all - except for the handful of actual experts here - amateurs at best, but probably ignorant peasants. Just about anything we have to say about it is just noise. I'd favor the positive noise, but that's just me.

Imagine being at a football game: "This game could easily be lost! Ah, see, another pass failed. Don't get your hopes up! Please don't cheer, please wait until the very last moment and then wait another hour to have administrative confirmation. Then wait two weeks. Then you may cheer, but only modestly."

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#256

Post by _0ffh »

vinnyvichy wrote: post #254
_0ffh wrote: post #240

Earlier quoted context omitted.

Ha, I've been talking about the same topic with an experimental physics professor friend of mine. He was just not interested at all, like "I've seen stuff like that so many times before, I'm not interested at this point. I may look at it when there's a publication in a serious journal." while I was like "Hey it's popcorn time, this is a fun ride, whatever the outcome!". =)

Speaking as an academic, I really hope they don't ever publish in a serious journal even if it turns out to replicate. Did your friend take Ranga Dias seriously because that was published in Nature? I understand there's a lot of noise, but one of the things one learns is to cut out noise without having to rely on journal brand

Nope, he didn't. You're getting the wrong message here.

That publication is necessary to arouse his interest doesn't mean it's sufficient to make him believe anything. Those are different things.

Peer review for publication is just meant to cut out the obvious crap. It's not a guaranty, and nobody who knows this stuff thinks it is.

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#257

Post by sampo »

tomohelix wrote: post #30

Summary of events so far: The claim: Room temp (~300K) superconductor exists and we got it! The replication attempts: The production method is so poorly documented only a fraction of the samples being made shows any interesting properties. And among those interesting ones, results varies. Very few, if any, attempt actually completely shows the entire spectrum of properties and behaviors of a true superconductor at ro…

> The production method is so poorly documented only a fraction of the samples being made shows any interesting properties.

I have understood that rather, the production method is poorly known even to the Koreans themselves, and also they have only a small success rate in their samples. So it's more that the Koreans themselves are not entirely sure what "makes it click", and you can't document it well because you don't yourself know all the details.

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#258

Post by [deleted] »

SanderNL wrote: post #255
jcranmer wrote: post #74

Earlier quoted context omitted.

> Worst case scenario, we got another class of high temp (warmer than liquid nitrogen but cold enough that applications are limited) superconductor but nothing revolutionary since at this point, it is pretty conclusive that there is something interesting with LK-99. I don't think that's the worst case scenario. The worst case scenario is that there is actually nothing interesting with LK-99, and everything we've seen…

It's good to keep an open mind both ways, but "skepticism" without either interesting or convincing arguments is IMO just as useless. We all know there is a good chance it turns out to be a dud. We all know cold fusion/emdrive/superluminal experiments turned out to be duds. We all know this. I wonder what news do "skeptics" have to bring to the table. Nothing a skeptic has to say changes anything. We are all - except…

[deleted]

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#259

Post by daemontus »

I see a lot of "This must be real, why would labs publish this if they don't think it's real, they have nothing to gain." sentiment on HN lately. Or "Researcher's career would be ruined if they falsely claim to replicate.", and so on. I also want to believe! But I should add a bit of skepticism to the hype :)

- "this could ruin their career": Depends. If they posted completely fake numbers or intentionally fake videos. Sure, that would be bad. But none of this is peer reviewed, and all of this can be retracted. A contaminated sample? Oops, retract. Bad measurement methodology? Oops, retract. Sure, somebody will remember that you made the controversial paper in the first place, but as long as you are not provably fabricating, a lot can be attributed to "an honest error". There are tons of peer reviewed papers out there with errors that completely change the outcome. Does not mean the authors are "finished".

- "they have nothing to gain": Oh, they absolutely do. While "science should be fully objective", funding agencies very much aren't. Obviously, just like VC funding, science funding is not a complete coin toss. But having "the right" team and background is often as important as the idea itself. One way to get the right background is to "touch shoulders with the giants" and one way to get the right team is to be highly visible and attract talent.

So overall, if LK99 is eventually shown to be a superconductor by someone else, you have a lot to gain, even if your own initial study is not perfect.

Let's say your team synthesised something. It looks like LK99 and it has some properties that are not really superconducting but at least a bit unusual. This clearly isn't what you hoped for. Now, do you run a bunch of other controls to see if it is some form of contamination, process error, combination of both... or do you publish a vague click-bait paper on ArXiv and hope that other results will somewhat align with yours?

Finally, I'm not claiming this paper or any other paper intentionally published untrue or misleading results. Just that scientists are also people. They have FOMO, they follow trends, they see what they want to see. As always, big claims require big evidence, and so far we don't really have that. But that does not mean there isn't some truth to the big claims :)

Re: Observation of zero resistance above 100 K in Pb₁₀₋ₓCuₓ(PO₄)₆O

#260

Post by criddell »

Filligree wrote: post #229
aziaziazi wrote: post #224

Earlier quoted context omitted.

> human tissues > isolated wires > alternated sheets The thinks you describes are systems made of multiple materials. Are you aware of a materials that behave that way by its own ?

No, and LK-99 isn’t made of a single material either.

How do you mean? It isn’t like a wire where you typically have separate insulator and conductor materials, is it?
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