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Comment by deyiao | Hacker News Reader

The optimistic aspects are: 1. The diamagnetism of LK-99 is very strong; 2. In almost all experiments, LK-99 has only exhibited one-dimensional diamagnetism, which is hard to consider as fraudulent coincidence; 3. One-dimensional diamagnetism is very mysterious, and there is currently no suitable theoretical explanation.

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It has been noted that graphite also exhibits "one-dimensional diamagnetism" (in the sense that it has much stronger diamagnetism in one plane than the other two) and it levitates fine and isn't very mysterious. There also haven't been any reliable measurements of strong diamagnetism in LK-99. We have the video from the team, which is not evidence of diamagnetism let alone strong diamagnetism, and we have a handful of magnetic susceptibility tests from labs on tiny, tiny samples (much smaller than the one in the video) that found weak diamagnetism.

I don't really think anything about LK-99 is optimistic at this point, honestly.

Is it one-dimensional (linear) or two-dimensional (planar)?

Wouldn’t two-dimensional (planar) superconductivity lead to one-dimensional (linear) diamagnetism? If the eddy currents are stuck in a plane then the induced magnetic field should be perpendicular to that plane, no?

Hyun-Tak Kim, one of the Korean authors, says it's a one dimensional superconductor.

How can there be eddy currents in a 1D superconductor? And if there are no eddy currents, wouldn’t that prevent diamagnetism?

I don't think there is any experimental evidence for that, and the original 1996 theory paper looks sketchy from what I managed to understand (it talkes about van der Waals transition and it is unclear for me where zero resistance would come from in that case)

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