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Comment by subzel0 | Hacker News Reader

I don't see why people go crazy over this, the meissner effect in superconductors look different.

I don't understand what you're not seeing. Nobody is saying that the whole LK-99 sample is superconducting. Why would you expect the whole sample to float, instead of "partial floating" as we're seeing, if you have a material that's only partially superconducting?

I was wondering this, why do all the samples not completely float. If the sample is only partially superconducting, could you just smash it into smaller pieces and find a few floating ones? Or would the different domains be so small that you have to turn the sample into dust before you get a completely superconducting piece? Probably can not be answered in general as it heavily depends on the synthesis process?

That's what is currently being done! A few videos have surfaced of smaller grains of LK-99 fully levitating. We're waiting for additional confirmation.

洗芝溪 answered this on Zhihu. All his answers are extremely good. This user knows something.

这应该还是材料的各向异性, 也就是它的准一维结构导致. 因为材料当中有一个固定晶相, 那个方向的抗磁性最强, 所以磁感线总会沿着这个方向走, 导致所有样品都是竖起来的.

This should be due to the anisotropy of the material, that is, its quasi-one-dimensional structure. Because there is a fixed crystal phase in the material, that direction has the strongest diamagnetism, so the magnetic field lines will always go along this direction, causing all The samples are all upright.

https://www.zhihu.com/question/615044128/answer/3145337312

If the material is a one-dimensional superconductor where current can only flow with zero resistance along one direction, aligning that direction with the magnetic field lines should produce the weakest diagmanetism, because the magnetic force is proportional to the cross product of current and magnetic field. If the two are parallel, the force is zero.

Of course this could explain why the sample doesn't lift off: it starts out with the superconducting direction at an angle to the magnetic field and relatively strong diamagnetism leading to a righting force until the two directions are nearly aligned and the diamagnetism is too weak to overcome gravity.

Someone asked:

> If you were to cut off the part that isn't lifting, do you reckon the entirety of the floaty half would float? AKA is this semi-float thing a purity issue?

And Andrew responded [0]:

> We wanted to do rock surgery, but I was scared we would shatter our biggest piece. It definitely has a piece that isn't contributing lift.

I'm guessing once they've prepared more samples and had existing samples tested they'll break some into smaller parts to try and get a piece that floats independently.

[0] https://twitter.com/andrewmccalip/status/1687408423179370497

https://twitter.com/andrewmccalip/status/1687419542103101442...

That batch seems to be a dud:

https://twitter.com/andrewmccalip/status/1687425301184393216

"Reaction looks like garbage. Very incomplete"

The Russian molecular biologist “Iris” had a tiny speck that floats, and there was another video as well (I don’t remember the source, but I saw it on Twitter). However, the credentials of the people or the labs they work for are unknown, so take it with a grain of salt.

Imagine you take red paint and blue paint and mix it together. It is certainly true that there is red paint and blue paint still in there, but however small samples you take it’s still going to be purple. You might get some samples that are reddish purple and some that are bluish purple however.

I thought it was clear that the process for creating the material is low yield, and the reaction produces other materials, so most of the material we're seeing is not LK-99. See the wiki section on synthesis: https://en.wikipedia.org/wiki/LK-99 . Right now we don't have a good way to produce the material with better yield.

So if we increased the magnitude of the magnetic field (e.g. by using an electric magnet), why couldn't we still have the sample float? Or does the Meissner effect not relate to the magnitude of the magnetic flux?

Unless, of course, the other end is attracting the magnet.

Some speculate its a monocrystsline "1D" superconductor, which could explain its different behavior.

But that is out of my depth. I am still trying to wrap my head around a directional superconductor/resistor...

I'm guessing this is the crappy v1 that barely does what it's supposed to. Still represents a giant leap for mankind

How so?

The rock should float for a start.

Meissner Effect does not mean it has to float. It only floats if thats the easiest way to expulse the magnet field. Otherwise it aligns normally with the magnetic field, which is supposedly happening here.

As it’s been theorized elsewhere, it may be that the production processes produce a material with only bits of the theorized superconductor in it, leading to the wiggling effect we see here as well as the Chinese replication video.

It is not a purity issue. On the other hand, 1D superconductors are expected to behave this way. See my other comments.

How do we know it isn't a purity issue?

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