First order transition in [LK-99] containing Cu2S

Interestingly Iris Alexandra suggested the levitation of LK-99 could be attributed to Cu2S before:

https://www.nextbigfuture.com/2023/08/iris-alexander-better-...

https://twitter.com/sanxiyn/status/1689151051239399424?t=12F...

Says patent shows three transitions.

They measured the resistivity of a pure Cu2S sample, a sample S1 containing 95% LK-99 and 5% Cu, and a sample S2 containing 30% LK-99 and 70% Cu2S.

The resistivity of the Cu2S sample has a drop of 3 to 4 orders of magnitude at about 390K (when temperature decreases). In the S2 sample the drop is much smaller, only factor 5. In S1 there is no such drop. Here the resistivity always falls with increasing temperature.

Then they write in the conclusion: "The superconducting-like behavior in LK-99 most likely originates from a magnitude reduction in resistivity caused by the first-order structural phase transition of Cu2S."

Since resistivity drop in LK-99 with temperature is about factor 10 according to https://arxiv.org/pdf/2307.12037.pdf Fig 5, that would mean that Sukbae Lee et al's specimen was composed of more than 70% Cu2S, which is unlikely.

The resistivity drop with decreasing temperature is not the only "superconducting-like behavior in LK-99". There is also a resistivity drop with decreasing current density and magnetic field at constant temperature. That cannot be explained with a phase change.

> The superconducting-like behavior in LK-99 most likely originates from a magnitude reduction in resistivity caused by the first-order structural phase transition of Cu2S. [...] It is important to note that this first-order structural transition differs significantly from the second-order superconducting transition.

The wag who dubbed various false alarms of room temperature superconductivity in the 1990s as USOs (Unidentified Superconducting Objects) got it quite right.

First there is the condensed-matter equivalent of blurry photos of floating saucers (or small disks like here) and lots of excitement, followed by investigations either not seeing anything or identifying the objects as weather ballons. The social media reaction is also similar.

This preprint identifies a weather balloon that was conspicuously close the site of the original photographs.

A quick look at the plots make me think this paper is legit and lk-99 is not a superconductor. Nice plots covering down to low temperature, unlike the original lk-99 papers which always seemed bizarre to me.

Is this based on a sample from the original lab or a new sample they synthesized?

I think this puts the nail in the coffin. It's over. However, gentlemen, shitposting with you during this whole travesty of science has been the greatest honor of my life.