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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

#141

Post by declan_roberts »

clmay wrote: post #103
rishav_sharan wrote: post #99

Naive question, and I hope someone more knowledgeable than me can enlighten me here; Why are we even testing for superconductivity with levitation, instead of just checking for current loss/heat loss while conducting?

This question has been asked with near identical or very similar wording in almost every LK-99 submission I've seen over the last week or so... Is there something botnet-y happening? I find it hard to believe anyone reading similar threads could have missed the numerous answers to this and similarly-formed questions that have been offered lately.

Not all of us read HN every day or follow each discussion. A lot of people don’t read the comments at all.

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

#142

Post by ThePhysicist »

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 are just one requirement for superconductivity, the other is that the ground state can actually form and won't be destroyed by thermal noise. However, the strong electron-phonon interaction required for (classical) superconductivity also makes the system susceptible to thermal noise, and in my opinion the thermal noise level at 290 K is just too much even for an ideal superconducting material.

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

#143

Post by ilitirit »

versteegen wrote: post #10
m3kw9 wrote: post #8

Has anyone even seen a ferromagnet stand up like that in a magnetic field?

Yes. https://nitter.net/VanGennepD/status/1688052003216261120 And this new paper finally rigorously explains away all the half-levitation videos. They can no longer be considered any evidence of SC at all.

Out of interest - has this new paper been peer reviewed already?

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

#144

Post by hcks »

joe__f wrote: post #120
ldjkfkdsjnv wrote: post #38

I knew it was fake, there would have been a huge rise in the stock market. Financial markets would have sniffed this out. The market never lies. If anything, this was an obvious opportunity to short it on prediction markets.

You're saying that, if this had been real, the stock market would have known about it before the scientific community? How exactly? The markets do predict things but they can't synthesise correct information out of nowhere. Wall Street stock brokers weren't exactly going to sit down and start trying to replicate these results to see if they could cash in on it

Contrary to bored laymen on the internet willing to believe anything for escapism, the stock market usually reflect the outside view base probabilities (~0% in the case of LK-99 being real)

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

#145

Post by fsh »

throwawaymaths wrote: post #90
Jweb_Guru wrote: post #46

Earlier quoted context omitted.

There is, a combination of strong (but not amazingly strong) diamagnetism at low field strengths and soft ferromagnetism (in floating samples) at high field strengths. Which is exactly what the paper in the link observed while getting the same results everyone else has. The only unambiguous sign of superconductivity was the original resistance graph which can apparently be explained by contact issues with four point…

Doesn't diamagnetic levitation require a specific arrangement of the permamagnets that is not recreated in these videos?

This is explained in Fig. S2 in TFA.

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

#147

Post by faraggi »

Jweb_Guru wrote: post #62
canadiantim wrote: post #59

Earlier quoted context omitted.

Resolved in which way?

It's not a room temperature ambient pressure superconductor. I should probably bet on it while there's still some value left here, I guess.

Seeing how sure you are of this, you should go all in.

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

#148

Post by carabiner »

ironborn123 wrote: post #132
versteegen wrote: post #95

Very interesting comments on the paper by Prof. Michael S. Fuhrer https://nitter.net/i/status/1688755932275384320 > But I think they buried the lede a little. Ferromagnetism is novel and unexpected in this material system, and might be interesting. But strong diamagnetism even more so > Even if the diamagnetic fraction is the entire sample (appears less) then it would be the second-strongest diamagnet known (and pyro…

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…

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

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

#149

Post by doubleunplussed »

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…

Andrew is mistaken, the paper he cites doesn't say that levitation is possible in a dipole field. Brauenbecker showed that diamagnetic levitation was possible at all (e.g. in a quadrupole field), but not in a dipole field.

Stable levitation in a dipole field is still thought to be something only type II superconductors can do, and Andrew should not uncritically repeat what he read on /sci/ - which is one of the only other google results for "Brauenbecker extension" currently (after his tweet).

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

#150

Post by lifthrasiir »

Jweb_Guru wrote: post #115
lifthrasiir wrote: post #69

Earlier quoted context omitted.

> They were refusing to share them with anyone reputable until today. This is incorrect (under some definition of "reputable"), because KENTECH [1] has reportedly received samples from Q-Center for the analysis, which started on July (following the MOU on May) and is estimated to finish within 6 months. Whether KENTECH is reputable or not, and whether it should be considered affiliated with Q-Center is of course deba…

I don't consider a replication attempt with a lab in a commercial relationship with another lab, that has essentially embargoed the results for six months, credible.

Of course, but you don't waste your lab time with useless samples. KENTECH must have seen something to actually allocate resources for the analysis. The recent interview with the vice president of KENTECH said that the initial request was in 2017, when samples were not really reproducible and too impure for analysis, but it was only this year when samples are good enough and can be actually analyzed---if it's just a fake they could have done so in 2017 instead.
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