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Ferromagnetic half levitation of LK-99-like synthetic samples

arxiv.org

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Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#201

Post by whimsicalism »

ThePhysicist wrote: post #142
hliyan wrote: post #80

According to this: https://twitter.com/Andercot/status/1688598313497694208 "...there is a less well-known exception to this rule called Brauenbecker extension which provides a mathematical proof that levitation is possible with a simple diamagnetic in a dipole field so long as the diamagnetic material mass is very small relative to the strength of the magnetic field." I was very hopeful in the early days and was foll…

Maybe a cautionary reminder to not listen to random influencers on Twitter. The expert community was really silent and reserved from the beginning as they've seen such wonder materials many times. Having worked in that field for many years I'm personally skeptical that there ever will be an ambient-pressure, room-temperature superconductor. The band structure and interactions that need to be present in the material a…

But the high temp cup rate superconductors don’t follow classical landau theory afaik

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#202

Post by whimsicalism »

kzrdude wrote: post #200
VHRanger wrote: post #4

After reading the r/physics thread on LK-99 [1] I've cooled significantly on the matter. Basically: people who work in SC think the initial science seems very sloppy and the replication attempts don't come close to what you need to demonstrate a RT SC [1] https://www.reddit.com/r/Physics/comments/15i3h9d/lk99_megat...

Now, I don't have this guys credentials, but it sounds very close to "This is not a superconductor as we know them to be". Which almost goes without saying, because if this is a room temperature superconductor in some sense, maybe something quite different is needed to explain it. I think we should be excited for new physics.

No, not at all. Meissner effect is constitutive of SC

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#203

Post by bnralt »

whimsicalism wrote: post #196
carabiner wrote: post #148

Earlier quoted context omitted.

I too like to assign probabilities to my vibes. Much more legitimate.

I think this culturally comes from lesswrong and it really makes me laugh every time I see it

Yeah, Scott Alexander wrote a whole article about how people should use made up fake statistics instead of simply saying "I don't know"[1].

[1] https://slatestarcodex.com/2013/05/02/if-its-worth-doing-its...

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#204

Post by moonchrome »

ThePhysicist wrote: post #142
hliyan wrote: post #80

According to this: https://twitter.com/Andercot/status/1688598313497694208 "...there is a less well-known exception to this rule called Brauenbecker extension which provides a mathematical proof that levitation is possible with a simple diamagnetic in a dipole field so long as the diamagnetic material mass is very small relative to the strength of the magnetic field." I was very hopeful in the early days and was foll…

Maybe a cautionary reminder to not listen to random influencers on Twitter. The expert community was really silent and reserved from the beginning as they've seen such wonder materials many times. Having worked in that field for many years I'm personally skeptical that there ever will be an ambient-pressure, room-temperature superconductor. The band structure and interactions that need to be present in the material a…

I don't see anything bad with this hype cycle :

  - these guys thought they found something
  - turns out it probably wasn't superconductors but it's an still interesting finding
  - there was no fraud and something new was discovered
  - material science got a bit more mainstream exposure
I'd rather see that than another crypto or AI hype cycle

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#205

Post by ironborn123 »

layer8 wrote: post #192
ironborn123 wrote: post #132

Earlier quoted context omitted.

There are 2 things in favor of the Korean team - Hyun-Tak Kim is unlikely to ruin his career and legacy for something careless and frivolous. But stranger things have happened, so lets assign a 10% probability to give some benefit of doubt to the team. - The various DFT papers show interesting flat band structures. But DFT is an approximation and also they do not take into account electron electron correlations. So l…

That's not how probabilities combine.

You are right, but probability estimation of possibly novel phenomena is an ill posed problem.

So either you do not model it at all, or come up with some mental model of what probability you are comfortable with and due to which factors; the factors being more important than the final number.

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#206

Post by exmadscientist »

moonchrome wrote: post #204
ThePhysicist wrote: post #142

Earlier quoted context omitted.

Maybe a cautionary reminder to not listen to random influencers on Twitter. The expert community was really silent and reserved from the beginning as they've seen such wonder materials many times. Having worked in that field for many years I'm personally skeptical that there ever will be an ambient-pressure, room-temperature superconductor. The band structure and interactions that need to be present in the material a…

I don't see anything bad with this hype cycle : - these guys thought they found something - turns out it probably wasn't superconductors but it's an still interesting finding - there was no fraud and something new was discovered - material science got a bit more mainstream exposure I'd rather see that than another crypto or AI hype cycle

No, it really wasn't that bad.

The annoying part, at least for me as someone who, uh, I guess used to go to a lot of colloquia on this stuff?, is the part you left out: people pre-judged the outcome (of all three phenomena you mention!) and then got really, really cranky with anyone who dared challenge their position.

If you (generic rhetorical you) want to believe that LK99 is going to superconduct, or that Bitcoin is going to the moon, or that AGI is coming next week, that's great. Really, it is! And you're allowed to talk about it, and put your money where your mouth is, and all that. What you're not allowed to do is get mad at people who respectfully disagree with you and point out why your dumb arguments are dumb. And you really, really, really need to pay attention, and not get more hostile, when your position starts to get falsified, as is/was helpfully possible for LK99 (but not so much those others). Do not hold fast to false things.

I understand that this is difficult when the people taking the other side are being equally awful, but such is life. We need to rise above, not get dragged down, lest everything fall into the same cesspools as contemporary politics.

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#207

Post by ajnin »

foven wrote: post #183
Double_a_92 wrote: post #170

Earlier quoted context omitted.

Because the levitation is a much better proof. It can only levitate if the resistance is really exactly 0. While measuring it somehow always adds errors, because the probes themselves have resistance. And then you can't be sure if it's 0 or just really low.

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).

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#208

Post by netheril96 »

exmadscientist wrote: post #206
moonchrome wrote: post #204

Earlier quoted context omitted.

I don't see anything bad with this hype cycle : - these guys thought they found something - turns out it probably wasn't superconductors but it's an still interesting finding - there was no fraud and something new was discovered - material science got a bit more mainstream exposure I'd rather see that than another crypto or AI hype cycle

No, it really wasn't that bad. The annoying part, at least for me as someone who, uh, I guess used to go to a lot of colloquia on this stuff?, is the part you left out: people pre-judged the outcome (of all three phenomena you mention!) and then got really, really cranky with anyone who dared challenge their position. If you (generic rhetorical you) want to believe that LK99 is going to superconduct, or that Bitcoin…

> really cranky with anyone who dared challenge their position.

You could profit from those people, if you are confident in your position, by shorting some of the stocks that shoot up from people's pre-judgments on this matter.

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#209

Post by jacquesm »

jszymborski wrote: post #64
jacquesm wrote: post #31

Earlier quoted context omitted.

These sort of answers do not inspire confidence. That looks like a play for time, why would they connect those two, it's clear they have priority locked in if the sample works out, the peer review of their paper is secondary to the questions of whether or not it is the real deal or not.

> These sort of answers do not inspire confidence. I'm not anything close to a Materials Engineer, but at least in the (very different) fields in which I've published, it's very standard to not share material (e.g.: plasmids, bacteria, code, or datasets) until you've published. Pre-prints rarely have code or data available if the authors intend to publish elsewhere (again, in my field).

Ok, that may well be the explanation then. As long as those samples don't go missing...

Re: Ferromagnetic half levitation of LK-99-like synthetic samples

#210

Post by jacquesm »

EthanHeilman wrote: post #35
jacquesm wrote: post #15

Earlier quoted context omitted.

That's a good question and there is a lot of speculation about that but ultimately we just do not know. There is a whole tree that you can set up to track their reasons, the big branch at the beginning is labeled 'it doesn't work' (which obviously is a bit short on the confirming side, it may still have a 'fraud' and a 'true believers' branch but that's academic) and then from the other branch you get branches which…

They weren't ready to publish and then got forced into the lime light by a member of their team going rogue. We should give them some benefit of the doubt due to the circumstances, even if LK-99 turns out not to be a SC, they didn't choose to publish.

Oh I definitely do give them the benefit of the doubt. Regardless of what is going on as long as it eventually works as advertised it's all fine and as long as their samples don't go missing they have a way out that's pretty easy.
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