Sukbae Lee, Jihoon Kim, Hyun-Tak Kim, Sungyeon Im, SooMin An, Keun Ho Auh
Abstract
A material called LK-99, a modified-lead apatite crystal structure with the composition Pb$_{10-x}$Cu$_x$(PO$_4$)$_{6O}$ ($0.9<x<1.1$), has been synthesized using the solid-state method. The material exhibits the Ohmic metal characteristic of Pb(6s1) above its superconducting critical temperature, $T_c$, and the levitation phenomenon as Meissner effect of a superconductor at room temperature and atmospheric pressure below $T_c$. A LK-99 sample shows $T_c$ above 126.85$^\circ$C (400 K). We analyze that the possibility of room-temperature superconductivity in this material is attributed to two factors: the first being the volume contraction resulting from an insulator-metal transition achieved by substituting Pb with Cu, and the second being on-site repulsive Coulomb interaction enhanced by the structural deformation in the one-dimensional(D) chain (Pb2-O$_{1/2}$-Pb2 along the c-axis) structure owing to superconducting condensation at $T_c$. The mechanism of the room-temperature $T_c$ is discussed by 1-D BR-BCS theory.
1. Is LK-99 a cuprate given Pb(10-x)-Cu(x)(6O) (0.9< x < 1.1)? I assume this is why BR-BCS theory is used to discuss. But aren't there known issues with BR-BCS?
The on-site Coulomb interaction would need to be very strong and infinite. However, the on-site Coulomb interaction is always finite in reality.
The disorder in real materials would likely prevent the formation of Cooper pairs.
Cooper pair formation mechanism is absent in these theories.
2. Whats the explanation for the partial levitation.
Levitation is obviously a very strong argument, but not bullet proof. It's known to exist for example in non-superconducting graphite (@ 6'40''): https://www.youtube.com/watch?v=TlD12QObooc
There are many groups trying to reproduce these data. Perhaps, the fastest way would be for the authors of this work to send samples around to others - that would relieve concerns.
galactic
Can you mention any specific groups working on replicating these results?
mattgentz03
@galactic the paper shows that creating the LK-99 metal took 72 hours, so I don't think we'll know for certain until the end of the month. On the plus side, though, it looks like lots of labs can do this, since it's frankly ridiculously cheap. An experienced metallurgist(?) could probably make this for under $250.
Erik
The graphite only levitated cause it was in the groove between multiple magnets, that were layin next to each other. Seeing that here is only 1 magnet and he could freely move it around on it, so it wasnt multiple hidden magnets, i dont see this as a possibility.
In the annals of history, a monumental event unfurled, igniting the spark that set ablaze humanity's technological prowess, and thus, our journey commenced.
Not sure if the rather simple production method may be totally replicable. Though it seems it can provide a general direction towards the ultimate goal of room temperature room pressure superconductors?
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The video does not show levitation. One edge is supported on the permanent magnet. One could achieve the same thing with a material simply having a magnetic dipole strong enough to lift it, but not strong enough to flip it over. If he flipped the sample over and it was still lifted similarly that would be impressive. This is not impressive, and seems deceptive to me.
On the other hand, it does seem unlikely that all these researchers would be tossing their careers out the window just by hyping an easily disprovable scam though, so I am optimistic in spite of this very weak "demonstration" video.
n-chub
Well, did you notice the sample was 'partially levitating ' on 2 different levels? When the person tossed it with a pen it changed its angle but still did not level out. Permanent magnets imho would find a balance of forces position as the magnetic field density decrease with distance, so there should be a point of force balance, right? Doesn't it suggest a different phenomena from just two magnrtic dipoles?
Some earthling
I disagree with your conclusion, because when the sample is pushed it ends up a different location on the magnet further from center, so the field will have a different angle at the new location, which would cause exactly what is observed with a magnetic dipole material (like a chip off a weak magnet) as the dipole aligns with the field as much as possible against the friction of the points of contact and the weight of the sample. All they had to do was flip it over and if it still didn't lay flat that would be a good demonstration of the Meissner effect. What is in the video could maybe be due to Meissner effect, but is entirely indistinguishable from playing around with a couple permanent magnets.
Also, if you look closely there is what appears to be a tiny chip of sample material stuck to the edge of the magnet, as if it is attracted to the magnet magnetically. If that is a chip from the sample, it sticking there is perhaps counter to the stated conclusion. I'm not sure how a superconductor would behave on a surface that is parallel to the magnetic field (the edge of a magnet) but it would need to be magnetic to some degree to stick there like that.
Professor Hirsch -- It's great to see you chiming in on the subject, where you're clearly an expert with original views. We noticed that the authors cited your theory of hole superconductivity. We would appreciate your extended thoughts on this experiment.
One concern, which was pointed out by some is illustrated in this plot.FiniteR.png93.5 KB
a) Flip the sample. To eliminate magnetic dipole effect. b) Cut the sample in two to give us a fully levitating sample. c) Why was this not done before the video? Still leaves the possibility of an extreme diamagnetic material like graphite.
